Australian rainfall during El Niño and La Niña events

El Niño: 2015–16

SOI: Moderate to strong

SST: Very strong

The overall effect of this El Niño on Australia was weak to moderate, with the 13 months from April 2015 to April 2016 (Figure 1) resulting in widespread areas of below average rainfall across central to southern Queensland, southeast South Australia, Victoria, and Tasmania. Dry conditions were already in place in Queensland and southeastern Australia in the lead up to this El Niño.

After sea surface temperatures in the central tropical Pacific Ocean came close to El Niño levels in 2014, the central tropical Pacific Ocean was primed for El Niño in 2015. Westerly wind events in January and March led to rapid ocean warming during autumn 2015, reaching El Niño levels during mid-April. Further westerly wind bursts consolidated the event in May and June. Rainfall was below average over parts of eastern Australia during April to August 2015 (Figure 2), although very warm sea surface temperatures (SSTs) in the eastern Indian Ocean may have offset some of the drying effect of the El Niño pattern in the Pacific. Warmer waters in the eastern Indian Ocean may provide extra moisture for rain-bearing systems as they cross Australia.

Between late August and mid-November a positive Indian Ocean Dipole (IOD) developed, further suppressing rainfall over much of Australia. The combination of the positive IOD and El Niño saw widespread below average rainfall during September and October 2015 (Figure 3). Rainfall was the equal fourth-lowest on record for Australia during September, and Tasmania had its driest spring on record. Mean temperatures for Australia were also highest on record for October to December 2015.

Below average rainfall persisted over much of eastern and northern Australia during the first four months of 2016 (Figure 4), with large parts of the northern coastline recording rainfall in the lowest 10% records. The event finally broke down during May 2016.

Peak values of central tropical Pacific SSTs and NINO indices exceeded +2 °C, placing this event alongside 1982 and 1998 as one of the strongest events on record. NINO3.4 reached +2.5 °C in November 2015.

This very strong El Niño contributed to an early start to the 2015–16 southen fire season, a markedly drier than average northern wet season, the weakest and least active tropical cyclone season on record (record low 3 TCs in 2015–16 season, none reaching category 3 strength), and prolonged heatwaves across Australia during autumn 2016. As the event started to break down very warm ocean water was pushed towards Australia. Combined with a delayed monsoon and cloudless skies this resulted in the worst coral bleaching event on record for the Great Barrier Reef. For more information on the effects of this El Niño see Climate Update El Niño is over, but has left its mark across the world.

Figure 1. Apr 2015 to Apr 2016
Figure 2. Apr 2015 to Aug 2015
Figure 3. Sep 2015 to Oct 2015
Figure 4. Jan 2016 to Apr 2016

La Niña: 2010–12

SOI: Strong


The 2010–12 La Niña event consisted of two peaks over successive summers; the 2010–11 peak was one of the strongest on record, comparable in strength with the events of 1917–18, 1955–56 and 1975–76. In October and December 2010, and February and March 2011, monthly Southern Oscillation Index values were the highest on record (records commenced in 1876). The 2011–12 peak was weaker, but still of moderate strength, in both atmospheric and oceanic indicators.

2010 and 2011 were the third-wettest and second-wettest calendar years on record for Australia, with 703 mm and 708 mm respectively, both well above the long-term average of 465 mm. Combined, the two events yielded Australia's wettest 24-month period on record (April 2010 to March 2012, Figure 1), and wettest two-calendar-year period (2010–2012), with 1411 mm of rainfall, topping the previous record of 1407 mm in 1973–1974.

The first year of the event followed a typical La Niña pattern, emerging in autumn 2010 and strengthening over winter. A dry June in 2010 was followed by significantly higher than average rainfall over the nine months from July 2010 to March 2011 (Figure 2). The SOI weakened and returned to neutral values during winter 2011. The six months from April to September 2011 (Figure 3) were relatively dry over much of Australia under neutral ENSO conditions. The SOI rose, again in spring 2011 and above-average rainfall returned to most of mainland Australia for the six months from October 2011 to March 2012 (Figure 4), although totals were not as exceptional as during the 2010–11 period.

Flooding was widespread between September 2010 and March 2011. As well as severe flooding in southeast Queensland, large areas of northern and western Victoria, New South Wales, northwestern Western Australia, and eastern Tasmania were subject to significant flooding. Widespread flooding across southeast Australia resulted in a significant increase in mosquito-borne diseases; 1092 cases of Ross River Virus were detected in Victoria between January and April, and 151 cases of Barmah Forest Virus. The tropics also experienced some highly unseasonable rain events during late autumn and winter 2010, in what is typically the dry season. Abundant vegetation growth following high rainfall in the usually arid interior fuelled widespread grassfires in central and northern Australia between August and November 2011. Much of inland southern and far northern Queensland, most of New South Wales, northern Victoria, and central Australia experienced flooding at least once between late November 2011 and March 2012.

Several notable tropical cyclones occurred during the summers of 2010–11 and 2011–12. Severe tropical cyclone Yasi was the most significant – Yasi was the strongest cyclone to make landfall in Queensland since at least 1918 (also a La Niña year), crossing the coast near Mission Beach, between Cairns and Townsville, as a category 5 storm. Other notable cyclones during the two La Niña events included Carlos, Grant, and Lua.

Read more: "Record-breaking La Niña events: An analysis of the La Niña life cycle and the impacts and significance of the 2010–11 and 2011–12 La Niña events in Australia".

24-month rainfall deciles for April 2010 to March 2012.
Figure 1. Apr 2010 to Mar 2012
9-month rainfall deciles for July 2010 to March 2011.
Figure 2. Jul 2010 to Mar 2011
6-month rainfall deciles for April 2011 to September 2011.
Figure 3. Apr 2011 to Sep 2011
6-month rainfall deciles for October 2011 to March 2012.
Figure 4. Oct 2011 to Mar 2012

El Niño: 2009–10

SOI: Weak to Moderate

SST: Moderate

The overall effect of this El Niño was weak, with the 11 months from May 2009 to March 2010 (Figure 1) resulting in widespread areas of below average rainfall across WA alone. In fact, the Australian rainfall anomaly pattern was close to a complete reversal of that usually observed.

The initial phase of the El Niño had the largest negative impact, when the SOI signal was rather weak. Consistent with the typical El Niño impact on Australia, May to October 2009 (Figure 2) was rather dry over much of the country, with Queensland and the NT having large areas with rainfall in the driest 10% of the historical record. Further south in areas that expect winter and spring rains, the impact was not quite so marked. Eastern Victoria and most of NSW, except the northeast and north central areas had below average rainfall for the period, while western Victoria, southern SA, Tasmania and northeast and north central NSW had average to above average rainfall.

By November, the SOI signal strengthened and finally came into line with other major ENSO indicators, most notably the SST. Paradoxically this ushered in a wet period over the eastern half of the country. For the 5 months from November 2009 to March 2010 (Figure 3), the NT, SA, Queensland, NSW and Victoria all had areas of rainfall in the top 10% (decile 10). Being generally located inland of the Great Dividing Range, these decile 10 regions included some small parts of record high falls. Particularly active monsoon conditions occurred in February and March when a southward surge of tropical air brought heavy to flood rains across central and southern parts of the NT, southern Queensland and northeast NSW. Remnant moisture also produced heavy rains across southern NSW and Victoria. This period included the Melbourne Hailstorm on the 6th of March 2010.

So Australia's rainfall patterns had switched from being typical of El Niño well before the main ENSO indicators had shown strong signs of retreating to neutral values, although SSTs had been in slow decline since the end of December. A more emphatic sign was the 25.8 rise in the SOI from March to April 2010 which heralded the end of the event as far as broadscale indicators were concerned.

Figure 1. May 2009 to Mar 2010
Figure 2. May 2009 to Oct 2009
Figure 3. Nov 2009 to Mar 2010

La Niña: 2008–09

SOI: Weak to Moderate

SST: Weak

This weak La Niña was a very short, marginal event, with its greatest impact occurring across the north of Australia during the period August 2008 to April 2009 (Figure 1).

The La Niña began with close-to-average rainfall recorded over northern Australia during August to October (Figure 2) and below to very-much-below-average rainfall in the southeast. This was followed by a widespread wet November to December (Figure 3), with 62% of Australia recording rainfall in the two wettest deciles. Tropical cyclone Billy produced areas of highest on record falls during December in the region surrounding Wyndham in the NT.

In contrast, January to February 2009 (Figure 4) was very dry across much of southern Australia, with Victoria and SA having 94% and 65% of their area in the lowest decile of rainfall, respectively. This, coupled with two extreme heat waves during the same period, contributed to the Black Saturday bushfires, with 7th February 2009 being the hottest day on record for large parts of Victoria, including Melbourne.

9-month rainfall deciles.
Figure 1. Aug 2008 to Apr 2009
3-month rainfall deciles.
Figure 2. Aug 2008 to Oct 2008
2-month rainfall deciles.
Figure 3. Nov 2008 to Dec 2008
2-month rainfall deciles.
Figure 4. Jan 2009 to Feb 2009

La Niña: 2007–08

SOI: Weak to Moderate

SST: Moderate

This moderately strong La Niña had a moderate impact over parts of northern and eastern Australia where rainfall was in deciles 8–10 for the nine months from June 2007 to February 2008 (Figure 1). However, it was late in developing and anomalous in terms of the broad band of below-average falls from central to southeastern Australia, due largely to very dry conditions from August to October (Figure 2). As a result there was little significant relief from the long-term dry conditions which had plagued the southeast, especially the high rainfall areas of the Murray Darling Basin. June 2007 (Figure 3) brought decile 10 totals, including large areas with record-high falls, across most of the central and eastern tropics. Wet conditions also extended down the east coast where major floods occurred in the Hunter region of NSW and in Gippsland. More typical La Niña rainfall anomalies took hold from November, with the four months from November 2007 to February 2008 (Figure 4) being moderately wet through the east of the mainland, and the north of both the NT and WA. A few small regions in Queensland and NSW had highest-on-record falls for the four-month period.

9-month rainfall deciles.
Figure 1. Jun 2007 to Feb 2008
3-month rainfall deciles.
Figure 2. Aug 2007 to Oct 2007
1-month rainfall deciles.
Figure 3. Jun 2007
4-month rainfall deciles.
Figure 4. Nov 2007 to Feb 2008

El Niño: 2006–07

SOI: Weak

SST: Weak

During May 2006 to December 2006 (Figure 1), most of Australia was strongly affected by this weak El Niño, with large regions in the southern and coastal areas being in the lowest 10% of rainfall. Particularly, southern Victoria and northern Tasmania were very dry, receiving lowest on record falls.

These 8 dry months had a very strong impact when factoring in the lack of relief from the 2002/03 El Niño. This was especially obvious in the 2006/07 fire season, with the Great Divide Fires being the longest running bushfires in Victoria's fire history. They began by lightning strikes in December 2006, and ended in February 2007. These fires caused the worst bushfire smoke since records began, affecting those with respiratory conditions such as asthma. Furthermore there were widespread fires in New South Wales during this time.

A change in conditions occurred around January 2007, with January to May 2007 (Figure 2) having a return to average to above average rainfall for most areas. However the Melbourne region and southeast Queensland were exceptions, being plagued by ongoing dry conditions.

Figure 1. May 2006 to Dec 2006
Figure 2. Jan 2007 to May 2007

El Niño: 2002–03

SOI: Weak

SST: Weak to Moderate

This weak to moderate El Niño event had a very strong impact in Australia. The major 2002-03 drought had rainfall deficiencies over the period March 2002 to January 2003 (Figure 1) that ranked in severity and areal extent with the extreme droughts of 1902 and 1982-83. Practically all parts of the country were affected, and in southern areas this exacerbated the effects of several preceding years of dry conditions. The extreme dryness coincided with exceptionally warm conditions: maximum temperatures averaged Australia established new records in each of the seasons autumn, winter and spring by a wide margin for the post-1950 era. Severe bushfires in eastern NSW, Canberra, and the mountains of southeast NSW and eastern Victoria, and widespread water shortages, were some of the main effects. Widespread above to very much above average falls occurred in February 2003 raising hopes of a consistent period of wet weather to erase the effects of severe drought. However, this was not to be. Totals for the remainder of 2003 were insufficient in many areas to overcome existing rainfall deficiencies - especially in parts of Queensland and southeast Victoria where 2003 was another rather dry year (Figure 2).

Figure 1. Mar 2002 to Jan 2003
Figure 2. 2003

La Niña: 1998–01

SOI: Moderate

SST: Moderate

Although there was waxing and waning of intensity, the 35 months from May 1998 to March 2001 (Figure 1) can be considered one long La Niña phase. It had a moderate to strong effect on a large area of the country; the south coast and Tasmania being the only areas missing out on the heavy falls. The NT had over 97% of its area in the highest decile of rainfall, while a high percentage of WA received record-high falls. Record-high totals were also prevalent about the northern NT, northeast Queensland and on the northwest slopes and plains of NSW.

The May 1998 to March 1999 (Figure 2) period followed a typical La Niña pattern, both in terms of its timing from one autumn to the next and also with widespread above to very-much-above-average falls. The following six months from April to September 1999 (Figure 3) were considerably drier and seemed to mark a return to neutral conditions. However, the onset of the northern wet season saw a resurgence of La Niña conditions, with widespread heavy rain over much of the country for the eight months from October 1999 to May 2000 (Figure 4). A pattern similar to the previous year then recurred with a dry spell from June to September 2000 (Figure 5) prior to a wet six months from October 2000 to March 2001 (Figure 6). With an Australia-wide average of 698 mm, the calendar year 2000 (Figure 7) was the second wettest year since 1900; only 1974 (760 mm) was wetter.

Flooding was rife during the three-year period, with tropical cyclones such as Thelma in December 1998, Rona in February 1999, Vance in March 1999, Steve in February and March 2000, Sam in December 2000 and Abigail in February 2001 all causing significant flooding in their wake. Substantial crop and stock losses were caused by widespread flooding in NSW and Queensland during July to September 1998 (Figure 8). Some regions had as many as four separate flooding incidents during these three months. There were also numerous hailstorms during this La Niña, including the notorious Sydney hailstorm in April 1999, which is one of Australia's most costly natural disasters in monetary terms.

35-month rainfall deciles.
Figure 1. May 1998 to Mar 2001
11-month rainfall deciles.
Figure 2. May 1998 to Mar 1999
Figure 3. Apr 1999 to Sep 1999
Figure 4. Oct 1999 to May 2000
Figure 5. Jun 2000 to Sep 2000
Figure 6. Oct 2000 to Mar 2001
Figure 7. 2000
Figure 8. Jul 1998 to Sep 1998

El Niño: 1997–98

SOI: Strong

SST: Very strong

Over the 12 months from April 1997 to March 1998 (Figure 1), below average totals occurred across Victoria, east and north Tasmania, central & east NSW, eastern sub-tropical Queensland & southwest WA. Overall the impact would be classed as weak with crops benefiting from widespread falls in both May and September. Southern and eastern Victoria were the worst affected with much of the region having falls among the driest 10% on record for the 12 months. Rainfall was consistently above average in eastern Australia from April 1998 onwards.

Figure 1. Apr 1997 to Mar 1998

El Niño: 1994–95

SOI: Strong

SST: Weak to Moderate

Over the 10 months from March to December 1994 (Figure 1), rainfall was in the lowest 10% of totals across most of Queensland, NSW, Victoria, SA, NE Tasmania and southern WA. Falls were also below average over the southern half of the NT and much of WA. So the impact would be described as strong. Average to above average falls fell in parts of eastern Australia (especially NSW) in November and December, and then very heavy rain and flooding occurred over inland NSW, SW Queensland and northern Victoria in January effectively ending the event. However, there was another period of below average rain from February to April 1995 (Figure 2) before higher falls became re-established.

Figure 1. Mar 1994 to Dec 1994
Figure 2. Feb 1995 to Apr 1995

El Niño: 1993–94

SOI: Moderate

SST: Weak

Not a "classic" event by any stretch of the imagination. Despite the SOI staying in moderate negative values until October, the ocean signal was weak except for April and May 1993. The effect was very weak with above average falls occurring over eastern Australia in July, October, November, and December 1993, and then again in February 1994. In fact, it was so wet that large parts of NSW and Victoria recorded totals in the highest 10% of records for the 6 months from July to December 1993 (Figure 1). Against this though, it was a poor wet season in eastern and northern Queensland, particularly the 3 months from December to February (Figure 2).

Figure 1. Jul 1993 to Dec 1993
Figure 2. Dec 1993 to Feb 1994

El Niño: 1991–92

SOI: Moderate to strong

SST: Moderate to strong

A strong effect over Queensland with about three-quarters of the state recording decile 1 rainfall totals for the 9 months from March to November 1991 (Figure 1). It was the driest such period on record in parts of the Darling Downs. The northern half of NSW was also seriously affected with about half this region in decile 1 for the nine months. Further south totals were average to above, although the seasonal distribution was very uneven. In Victoria, southern NSW, and much of Tasmania, a very dry autumn was followed by a wet June-September period and then more below average falls in October-November. Above to very much above average rain fell in December over SE Queensland and the eastern half of NSW marking the beginning of the end of this event in these regions. Although falls were patchy in January 1992, heavy rain fell again in February, particularly in the southeast of Queensland and NSW. In the tropics though, totals were consistently below average from November through to April (Figure 2) with many areas of WA, the NT, and north Queensland recording decile 1 falls for the 6 months.

Figure 1. Mar 1991 to Nov 1991
Figure 2. Nov 1991 to Apr 1992

La Niña: 1988–89

SOI: Moderate


This was a strong La Niña which had a strong effect on the southeast half of the country, with April 1988 to July 1989 (Figure 1) rainfall in the highest decile for most New South Wales, much of South Australia and northern Victoria, and parts of southern and eastern Queensland. Much of Tasmania and western WA, together with parts of the far north also had falls in deciles 8 and 9 for this period. From April to December 1988 (Figure 2), above to very-much-above-average rainfall fell across much of the country, but there was a marked break to this pattern over January and February 1989 (Figure 3), when much of the continent recorded totals in the lowest three deciles. However, typical La Niña conditions returned with a vengeance during the March to July 1989 (Figure 4) period when there were widespread falls in decile 10, including record-high totals over a large fraction of SA.

Flooding was a regular occurrence during this La Niña, with flooding in Adelaide in May 1988, NSW, northern SA and western Queensland during July 1988, southeastern Queensland in September 1988, SA in March 1989 and central Queensland during April to May 1989. One of the more notable floods occurred in Victoria during November and December 1988 (Figure 5), with widespread flash flooding, particularly in the Melbourne and Gippsland areas. Several rivers broke their banks.

In December 1988 following the flooding, over 700 cases of Ross River virus were reported in Victoria, with the main affected area being the Gippsland region. In April 1989, following heavy rains in northeast Tasmania almost 60 cases of Ross River virus were reported.

Figure 1. Apr 1988 to Jul 1989
Figure 2. Apr 1988 to Dec 1988
Figure 3. Jan 1989 to Feb 1989
Figure 4. Mar 1989 to Jul 1989
Figure 5. Nov 1988 to Dec 1988

El Niño: 1987–88

SOI: Moderate to strong

SST: Moderate to strong

Generally weak with mainly average to above average falls in Victoria, NSW and Queensland during the 9 months from May 1987 to January 1988 (Figure 1). Northern and eastern Tasmania, pockets of Gippsland and the southwest corner of WA fared rather worse with totals in the lowest 10% for the 7 months from April to October 1987 (Figure 2). It was also a poor wet season over Cape York and northwest Queensland with decile 1 totals for the 6 months from October 1987 to March 1988 (Figure 3).

Figure 1. May 1987 to Jan 1988
Figure 2. Apr 1987 to Oct 1987
Figure 3. Oct 1987 to Mar 1988

El Niño: 1982–83

SOI: Very strong

SST: Very strong

A very strong impact on Australia with drought conditions widepsread across eastern and southern Australia. Below average rainfall patterns were established in April 1982 and continued almost unabated up to and including February 1983 when southern Australia experienced heat-wave conditions and bushfires that culminated in the Ash Wednesday disaster. For the 11 months from April 82 to February 83 (Figure 1) virtually all of the eastern two-thirds of the country recorded rainfall totals within the driest 10%. In fact, the vast bulk of Victoria, the southern halves of both NSW and South Australia, together with large tracts of central and western Queensland recorded record low falls for this particular 11-month period.

The pattern changed abruptly in March 1983 when flood rains in central and southern Australia heralded several months of above average rainfall across much of the country.

Figure 1. Apr 1982 to Feb 1983

El Niño: 1977–78

SOI: Moderate

SST: Weak

A moderate to strong impact, but of fairly short duration. For the six months from June to November (Figure 1), most of NSW, the southern half of Queensland, patches in northern Victoria and northern Tasmania, and scattered regions in both WA and SA recorded rainfall totals in the driest 10% for that 6-month period. Most remaining areas in these states, with the exception of SA, registered below average falls. Above average rain in January eased the situation in eastern Australia, but for the nine months from June 77 to February 78 (Figure 2), decile 1 totals were registered in northern Victoria, southern and far western NSW together with the northeast corner of that state, and SE Queensland.

Figure 1. Jun 1977 to Nov 1977
Figure 2. Jun 1977 to Feb 1978

La Niña: 1973–76

SOI: >Moderate to strong

SST: ?

Following a relatively intense El Niño, and in perhaps the longest sustained period of La Niña conditions in the instrumental record, this strong La Niña had a strong effect on Australia, with excessive rainfall over much of the country. For the period from June 1973 until March 1976 (Figure 1), rainfall was above average over virtually the entire country, with more than half of the area east of WA recording its highest rainfall on record for this particular 34-month period. The particularly impressive feature of the rainfall during this period was the complete lack of significant dry periods; only two short periods are worth noting – June to July 1974 and May to June 1975. With an area-average of 760 mm, 1974 was Australia's wettest year on record, while 1973 (651 mm) and 1975 (602 mm) were third and fifth wettest respectively.

The very wet 1974 (Figure 2) caused the most recent major outbreak of Murray Valley encephalitis in southeastern Australia, with 58 reported cases. Also during this La Niña, 400–500 cases of Ross River virus were reported, ranging in areas from South Australia's Murray Valley region, to Queensland. Most of these cases occurred in SA. The extensive rain in early 1974 produced abundant growth in central Australia, and when it dried out in late spring 1974 it provided abundant fuel for widespread fires.

In what was a remarkable period, the month of January 1974 (Figure 3) stands out, with record rainfall and widespread flooding in central and eastern Australia. In area-average terms it is the wettest month on record across Australia, the NT and Queensland, while it is the second wettest over SA and NSW. Many of the major river systems in these areas were flooded during this time. Towards the end of January, tropical cyclone Wanda crossed the coast near Brisbane and exacerbated the flooding in Queensland, including one of Brisbane's worst floods on record. Several other cyclones caused flooding, such as Una in December 1973, Zoe in March 1974, David in January 1976, Beth and ex-tropical cyclone Alan in February 1976, and Dawn in March 1976 to name a few.

Another standout month was October 1975 (Figure 4) during which Victoria had its wettest month on record and extensive flooding, and a large area with highest-on-record falls. Most other parts of continental Australia had rainfall in the top decile, except for southwest WA, northern NSW, southern Queensland and scattered areas in the NT.

Figure 1. Jun 1973 to Mar 1976
Figure 2. 1974
Figure 3. Jan 1974
Figure 4. Oct 1975

El Niño: 1972–73

SOI: Moderate

SST: Moderate to strong

Drier than average weather became established in the southern areas in March 1972, and apart from a brief respite in August, continued to the end of the year. Overall the impact would be classed as strong. For the ten months from March to December 1972 (Figure 1), rainfall totals were in the driest 10% of records (decile 1) over the majority of Victoria, SA, southern WA, north and east Tasmania, western and southern NSW, and far southwest and central Queensland.

Above average falls occurred in January, followed by widepsread above average to record falls in February, thereby ending the drought and heralding the wettest two-year period in Australia's history.

Figure 1. Mar 1972 to Dec 1972

La Niña: 1970–72

SOI: Moderate

SST: Moderate

This moderately strong La Niña had only a weak to modest effect on Australia's climate. Over the 22-month period from June 1970 until March 1972 (Figure 1), rainfall was above average over much of the area comprised of Queensland, NSW, Victoria, Tasmania and the southeast of SA. Tasmania was particularly wet, with most of the state having totals in the highest 10% of the historical record (decile 10), as did southwest Victoria, coastal SA and some parts of eastern Queensland.

Overall though, the rainfall was fairly patchy in terms of sustained high falls, while some notable dry periods occurred during the event. Apart from in Tasmania and southern Victoria, winter 1970 (Figure 2) was especially dry, with decile 1 totals in a broad zone extending across the centre of the country. Summer 1970–71 was drier than average over the NT, western Queensland, SA and eastern WA, while the March–June period in 1971 was much drier than average from southeast Queensland, through eastern NSW to East Gippsland.

There were several floods during this La Niña. In August 1970, 89% of Tasmania had monthly rainfall in decile 10, with flooding on the Deloraine and La Trobe rivers in the north of the state. Flash floods occurred in Canberra in January 1971, while in February of that same year, there was widespread flooding in the Gippsland area of Victoria, which caused large agricultural losses. March brought flooding in Broken Hill.

Several cyclones also contributed to flooding, notably tropical cyclone Dora in February 1971, which hit the Queensland coast just north of Brisbane. The affected region had highest-on-record falls for February. Another tropical cyclone, Althea, crossed the coast at Townsville on Christmas Eve 1971, causing $50 million damage (1971 dollars). Although it didn't cause particularly large amounts of flooding, the cyclone generated a 3.66 m storm surge and damaged or destroyed 90% of the houses on Magnetic Island. In the decile map for December (Figure 3), Althea’s path is quite clear, with the arc of the highest decile in Queensland showing its path.

There were also two outbreaks of Ross River Virus during this La Niña: one in December 1970 in Coleambally, NSW, with 33 reported cases, and another one in February 1971 in the Murray River region, with over 109 cases reported.

By February and March 1972, regions of below-average rainfall were becoming evident as the climate began a shift into El Niño.

Figure 1. Jun 1970 to Mar 1972
Figure 2. Jun 1970 to Aug 1970
Figure 3. Dec 1971

El Niño: 1969–70

SOI: Weak

SST: Weak

In this case, weak indicators lead to a weak effect through the region of eastern Australia most commonly affected. There were some dry months between June 1969 and February 1970, Figure 1, (notably June and October in Victoria), but for this 9-month period decile 1 totals were mainly confined to some of the border regions between SA and each of Victoria, NSW and Queensland. Parts of the Eyre Peninsula and southwest WA also had totals in the driest 10% of falls.

However there was a strong impact across most remaining parts of WA together with some adjacent regions in eastern NT. These areas recorded decile 1 or record low falls for the nine months from June '69 to Feb '70, but it is more than likely that an additional influence unrelated to El Niño was crucial to the development of this rainfall anomaly.

Figure 1. Jun 1969 to Feb 1970

El Niño: 1965–66

SOI: Moderate to strong

SST: Moderate

The overall impact was moderate. Over the 9-month period from March to November 1965 (Figure 1), rainfall was below average across most of NSW and SA, the southern half of Queensland, southern NT and patches in both Victoria and Tasmania. The most seriously affected region was a large area straddling the NSW/Queensland border stretching from near Longreach in the north to Dubbo in the south. Totals here were in decile 1 for the nine months with a few patches of lowest on record.

Above average totals occurred in August over SA and southern NSW, but it wasn't until December 1965 that some relief came for the worst affected area with above to very much above average falls. However, the relief was short-lived as conditions were generally drier than average right up until July 1966 causing a large part of NSW and southern Queensland to be in decile 1 for the 17 months (March 1965 to July 1966), Figure 2. This was depsite a rise in the SOI and a return to neutral Pacific sea-surface temperatures, thus suggesting a mechanism apart from El Niño.

Figure 1. Mar 1965 to Nov 1965
Figure 2. Mar 1965 to Jul 1966

La Niña: 1964–65

SOI: Moderate

SST: Moderate

This short-lived La Niña had a modest impact on parts of southern and eastern Australia. As the El Niño of 1963–64 came to an end, the SOI began rising during autumn, with widespread above-average falls during April, especially across the southern half of the country. However, May was very dry in southwest WA, while elsewhere in the south falls were rather patchy.

The June to October period was marked by above-average falls across the southern one-third of Australia, particularly about the exposed coast and ranges in the southeast. Record-high July totals were recorded near parts of WA's southern coast, in a large straddling southeast SA and western Victoria, and across Victoria’s northeast ranges into the Snowy Mountains of NSW. Above-average falls were widespread over Australia in September and October, especially the former when record-high totals were observed over much of central to southeastern SA and the adjacent parts of northwest Victoria and the far west of NSW.

For the seven months from April to October 1964 (Figure 1), rainfall was in deciles 8–10 over southern WA, western and northern Tasmania, Victoria, much of the southern two-thirds of SA, a majority of NSW and parts of both eastern Queensland and the north of the NT. In a few small patches in western Victoria it was the wettest such period on record.

Wet conditions persisted in the far southeast during November and December, but below-average falls prevailed over NSW and the southern half of Queensland as a prelude to the 1965 El Niño.

Figure 1. Apr 1964 to Oct 1964

El Niño: 1963–64

SOI: Weak

SST: Weak

This event seemed to develop a little later than is typical, with the main period of dryness being over the relatively short period from September 1963 to March 1964 (Figure 1). During this 7-month period the impact was weak across the Murray-Darling Basin, the most commonly affected area, but strong over regions further west. However, because this affected region was unusual, there is a strong probability that other influences helped to cause the anomalously low rainfall.

These seven months were exceptionally dry across SA, the southern half of the NT, eastern WA and the western fringes of Victoria and NSW. Large parts of western SA and southeast WA had record low falls for the period.

Figure 1. Sep 1963 to Mar 1964

El Niño: 1957–58

SOI: Weak

SST: Weak to Moderate

The overall impact was moderate to strong with most of the southern half of the continent being drier than average, including extensive parts of NSW, SA and WA that were in decile 1 for the nine months from March to November 1957 (Figure 1). Parts of central NSW and WA registered their lowest rainfall on record for this 9-month period.

May and the spring months were particularly dry, but falls were more patchy in winter with some above average regions in NSW and Victoria. Tasmania and western Victoria though, were drier than average in winter with record low falls in the Apple-Isle.

Figure 1. Mar 1957 to Nov 1957

La Niña: 1954–57

SOI: Moderate

SST: Moderate

This La Niña had a strong effect across the eastern third of Australia. From April 1954 until January 1957 (34 months) (Figure 1), Queensland, NSW and Victoria all had over 70% of their areas in the highest decile of rainfall, with parts of these areas being highest-on-record falls.

In February 1955 (Figure 2) extensive flooding occurred in NSW, with almost all of the state's river systems affected. As a result, 15 000 people were left homeless in the short term, 50 people died, 100 000 livestock died and there were large agricultural losses. Some of the worst flooding occurred at Branxton, just north of Newcastle, where flood waters were almost 4m deep, and towns such as Maitland were also largely inundated.

March 1956 to December 1956 (Figure 3) was a very wet period for the regions surrounding the Murray-Darling River System, with floods from May until December. 1956 was the wettest year on record for the Murray-Darling Basin. During this time there was a Ross River virus outbreak in April 1956, with over 2000 cases reported throughout South Australia, Victoria and NSW near the river system.

Figure 1. Apr 1954 to Jan 1957
Figure 2. Feb 1955
Figure 3. Mar 1956 to Dec 1956

El Niño: 1951–52

SOI: Weak

SST: Weak

The overall impact was strong with most of the northern two-thirds of the country recording below to very much below average rainfall. For the 12 months from March 1951 to February 1952 (Figure 1), rainfall totals were in decile 1 over nearly all of Queensland, the northern half of the NT, as well as scattered parts of northern NSW, SA and WA. Large areas in northern Queensland and the NT had record low falls for this particular 12-month period.

Rainfall was average to above average in Victoria and southern SA, particularly between April and August (Figure 2) when 5-month totals were in decile 10 or the highest on record.

Figure 1. Mar 1951 to Feb 1952
Figure 2. Apr 1951 to Aug 1951

La Niña: 1949–51

SOI: ?

SST: Moderate

A particularly wet La Niña, which probably classifies alongside 1916–1918 and 1973–1976 as those with the strongest effects. The oceanic signal of this event began in winter 1949 when cooling occurred along the equatorial Pacific, but it wasn't until December 1949 that a consistent SOI signal became established. For the time period from December 1949 until February 1951 (Figure 1), much of eastern and northern Australia recorded above to very-much-above-average rainfall. Notably, Queensland had 95% of its area in the top two deciles for this period, and NSW 76%, with significant parts being highest on record, especially over the eastern half of NSW. 1950 was the wettest year on record averaged over both Queensland and NSW as well as over the four eastern states that comprise eastern Australia, despite the fact that Tasmania had its eighth driest year on record.

Several cyclones hit the north-east coast in early 1950, with one in particular during March (Figure 2) causing widespread flooding. Winter 1950 (Figure 3) was especially wet in coastal NSW and southern Queensland, while spring 1950 (Figure 4) was wet across much of the region, with record falls across large parts of Queensland and NSW west of the Great Dividing Range.

The wet year of 1950 (Figure 5) also caused Murray Valley encephalitis to reappear in 1951, with 48 reported cases.

Figure 1. Dec 1949 to Feb 1951
Figure 2. Mar 1950
Figure 3. Jun 1950 to Aug 1950
Figure 4. Sept 1950 to Nov 1950
Figure 5. 1950

El Niño: 1946–47

SOI: Weak to Moderate


A strong impact over eastern and northern Australia with most of NSW, Queensland, and the north of the NT registering decile 1 falls for the 10 months from April 1946 to January 1947 (Figure 1). A large region in the central-west of Queensland experienced record low totals for this particular 10-month period. Large parts of SA, Victoria, and WA were also drier than average.

Areas of below average rainfall first became evident over Queensland in autumn and gradually spread southwards. However, there were some months when the dry spell was eased by useful rains - most notably across Victoria in July and the NSW/Queensland border areas in September. Average to above average falls were also prominent in November and December.

The pattern was broken in February 1947 when widespread heavy rain fell in the worst affected areas. Good follow-up falls also occurred in March.

Figure 1. Apr 1946 to Jan 1947

La Niña: 1942–43

SOI: Weak


For the first part of this La Niña, its effects were rather widespread from May to December 1942 (Figure 1), with most of the continent getting decent falls, and almost half of the area being in the top two deciles. The second part, however, was quite dry for eastern Australia, which had approximately half of its area in the bottom 30% of rainfall for January to April 1943 (Figure 2). Western Australia by comparison, fared better in this period, with above-average falls across most of the coast, and southwest WA. These above-average falls in WA were caused by several tropical cyclones making landfall during this period.

In the region around Darwin in the Northern Territory, 105 cases of Ross River virus were reported in November 1942. In the following November another 40 cases were reported in the Adelaide River area nearby.

Figure 1. May 1942 to Dec 1942
Figure 2. Jan 1943 to Apr 1943

El Niño: 1941–42

SOI: Strong


The overall impact was moderate to strong, particularly in NSW which was mainly in decile 1 for the 10 months from April 1941 to January 1942 (Figure 1). The southern tier of Queensland was similarly affected, as was Cape York in the far north of the State. The east and north of both Victoria and Tasmania were drier than average during this 10-month period with decile 1 falls in some areas.

The pattern began to change in February 1942 with a return to average falls or higher for the period up to mid-winter, although April 1942 was a dry month across the eastern half of NSW.

Figure 1. Apr 1941 - Jan 1942

El Niño: 1940–41

SOI: Strong


The overall impact was strong, although the period that was characterised by anomalously low rainfall was a little shorter than that which occurred with many other events. For the nine months from March to November 1940 (Figure 1) inclusive, most of the country recorded below average rainfall, the main exceptions being parts of eastern and northern Queensland and some areas in the NT. There were vast areas where falls were in decile 1, and this includes the above average rainfall that fell in April in NSW, Victoria and central Australia. For the shorter 7-month period beginning in May (Figure 2), one-half to two-thirds of the country recorded decile 1 rainfall totals.

Above average rainfall in eastern NSW and southeast Queensland in December heralded a change in the pattern. January 1941 was an excpetionally wet month over eastern Australia with decile 10 falls covering nearly all of Victoria and NSW, much of the southern half of Queensland and the eastern half of SA. Highest on record totals occurred in each state. March 1941 was another wet month and above average falls continued in the tropics until June.

Figure 1. Mar 1940 to Nov 1940
Figure 2. May 1940 to Nov 1940

La Niña: 1938–39

SOI: Moderate


A dry La Niña, especially so in the southeast. April 1938 to January 1939 (Figure 1) was very dry in Victoria, southern NSW and southeastern South Australia. Victoria had 98% of its area in the lowest decile, and southeast Victoria had lowest-on-record falls. When this low rainfall combined with extreme heat, it resulted in the Black Friday fires, which lit up almost all of Victoria, southern NSW and southeastern South Australia, causing massive devastation. Some 1.5–2 million ha was burnt in Victoria, much of it protected forest.

In the three months following Black Friday, February–April 1939 (Figure 2) these regions received rainfall in the top decile, some parts receiving record-high falls.

Figure 1. Apr 1938 to Jan 1939
Figure 2. Feb 1939 to Apr 1939

La Niña: 1928–30

SOI: Weak to Moderate


Another anomalously dry La Niña in Australia, with Tasmania and northern Australia being the only substantial regions to get above-average rainfall from August 1928–March 1930 (Figure 1). In South Australia it was the driest such period on record. In northern Tasmania flooding occurred in April 1929 (Figure 2). 14 people died when the Briscia Dam (on the Cascade River) burst; to date Australia's only failure of a major dam that has caused casualties. Flooding and livestock losses occurred as far south as Hobart.

Several cyclones also caused flooding in north-east Australia during this La Niña. Two hit the east coast within a week of each other in February 1929, causing widespread flooding. Another pair of closely spaced cyclones passed though again in January 1930 in northern Queensland. The first of this second pair of cyclones caused devastating flooding in most of the rivers between Cooktown and Townsville, while the second, late in the month brought heavy rains in which 10 000 livestock (cattle and sheep) drowned.

Figure 1. Aug 1928 to Mar 1930
Figure 2. Apr 1929

El Niño: 1925–26

SOI: Moderate


The impact would be classed as strong, but the main area affected was somewhat to the west of that most commonly influenced. For the 12 months from March 1925 to February 1926 (Figure 1), most of eastern and central Australia had below average falls with decile 1 to lowest on record values across most of Tasmania, Victoria, northern SA, southern NT and far western Queensland.

There was quite a deal of month to month variation in the rainfall patterns with May and June 1925 being wet or very wet over parts of eastern and central NSW. Other useful falls to occur during the period occurred as follows: July 1925 in East Gippsland, August 1925 in southeast Queensland, September 1925 in southeast SA and November 1925 across northern NSW. October, December and February were particularly dry over large areas.

With the exception of Tasmania and western Victoria, the dry weather pattern was broken by widespread and heavy rain in March and April 1926.

Figure 1. Mar 1925 to Feb 1926

La Niña: 1924–25

SOI: Weak


The initial three months of this La Niña, May to July 1924 (Figure 1) were rather dry, and the higher-than-average rainfall fell mainly in late winter and springtime. For August 1924 to January 1925 (Figure 2) much of eastern Australia, the NT and also southwest Western Australia had rainfall totals in the top 10%. A small section of central Queensland had highest-on-record falls. In May 1925, an east coast low caused exceptionally heavy but fairly localised rainfall, which resulted in flooding on the Murrumbidgee River and the coastal rivers of southern NSW, affecting southern NSW and the ACT, with Gundagai and Wagga Wagga severely affected.

The overall impact for this La Niña may be described as weak, with only slightly higher than normal rainfall for May 1924–May 1925 (Figure 3).

Figure 1. May 1924 to Jul 1924
Figure 2. Aug 1924 to Jan 1925
Figure 3. May 1924 to May 1925

El Niño: 1919–20

SOI: Weak to moderate


A classic event in terms of impact with strong rainfall deficits over the Murray-Darling Basin, Tasmania, western Victoria and the southeast of SA for the 15 months from March 1919 to May 1920 (Figure 1). Most of these areas recorded falls in decile 1 with areas of lowest on record featuring in central NSW. Although there were pockets that received decent falls from time to time during this period, the only widespread falls occurred in May and December. The driest months were June, July, October, November and February.

The SOI had been negative since late 1918 rising to around zero during the early part of 1920. However, it wasn't until the SOI rose to around +10 in June and July that the drought was eased or broken with widepsread above average falls.

Figure 1. Mar 1919 to May 1920

La Niña: 1916–18



Following the drought of 1911–1916, this long lasting La Niña produced highest-on-record falls for the 20-month period from June 1916 to January 1918 (Figure 1) in regions of SA, Victoria, Tasmania, WA, NSW and a large area of Queensland. All the eastern states and SA had well over half of their area with rainfall in the highest 10% of the historical record during this time.

Queensland was hardest hit by this La Niña. Heavy rain during December 1916 caused flooding in Clermont in which most of the town was destroyed or swept away. Following the flood the town was rebuilt on higher ground.

In addition, two intense tropical cyclones affected Queensland in early 1918. Now known as the Mackay cyclone, this storm drenched the central Queensland coastal town with 1411 mm of rainfall in three days. In March an even stronger cyclone made landfall over Innisfail, with widespread damage affecting the Cairns, Babinda and Atherton Tableland districts.

Heavy rain across Victoria in September 1916 not only caused extensive flooding, but aided in producing high wheat yields for the Mallee and Wimmera regions. In June 1917, there were floods in northeastern Victoria.

During the very wet year of 1917 (Figure 2), 114 cases of Murray Valley Encephalitis were reported in southeastern Australia, and another 67 cases in 1918.

Figure 1. Jun 1916 to Jan 1918
Figure 2. 1917

El Niño: 1914–15

SOI: Strong


This was the second year of a double El Niño event and the effect was strong. The SOI was generally in the −15 to −20 range from April 1914 to May 1915, and apart from coastal NSW virtually all of eastern Australia, together with the east of SA and southwest WA recorded below average rainfall. For the 12 months from May 1914 to April 1915 (Figure 1) decile 1 or lowest on record totals were particularly prominent in Tasmania, Victoria, southeast SA and southern NSW.

Dry weather set in with a vengeance in southeastern Australia in June and continued almost unabated until the end of October. The pattern spread northward into Queensland in August, although much of Victoria, NSW and Queensland had some relief in November and December with average to above average rains. The central and north coasts of NSW were very wet in September and October during which time record dry conditions occurred over Victoria and Tasmania.

The pattern of below average rainfall returned in January 1915 and continued to affect most of eastern Australia until the end of April. From May onwards the pattern reverted to one of average to above average falls that eventually led into the double La Niña event of 1916/1917.

Figure 1. May 1914 to Apr 1915

El Niño: 1913–14

SOI: Weak


A weak to moderate effect with most of southeastern Australia and parts of southern Queensland recording below average rainfall for the June 1913 to February 1914 period (Figure 1). Areas of decile 1 totals tended to be rather patchy, the largest covering parts of Gippsland, northeast Victoria and adjacent areas of the southern inland of NSW. The below average rainfall pattern took a while to become established with wet conditions prevailing over much of NSW between March and June 1913. However, June 1913 was very dry in far western NSW, SA and western Victoria and this pattern spread eastward in July. There were average to above average falls in September and October 1913, but rainfall tended to be below normal for the four months following this.

Figure 1. Jun 1913 to Feb 1914

El Niño: 1911–12

SOI: Moderate to strong


This event took a little while to get going in terms of rainfall anomalies, but for the 14 months from April 1911 to May 1912 (Figure 1) the overall impact was moderate to strong. For this period falls were in decile 1 over much of eastern Queensland, northern NSW, northern Victoria and the southern border areas of NSW, western WA and parts of both southeast SA and Tasmania. In parts of central Queensland, it was the driest such period on record.

Occasional good falls happened during the early and middle parts of the event with November and December 1911 being particularly wet across central NSW. However, January, April and May 1912 were dry over large areas. This pattern was broken in June and July 1912 with widespread above average rainfall.

Figure 1. Apr 1911 to May 1912

La Niña: 1909–11

SOI: ??


This La Niña had a rather localised yet strong effect, with high falls in coastal Queensland, southeast SA, western Victoria and south west WA during May 1909 to April 1911 (Figure 1). The rest of the continent received mostly normal falls for this period, except for central Western Australia, which had well below-average rainfall. During this time floods were frequent, with several events in the summer months in Queensland.

During August 1909 (Figure 2) northern and western Victoria, and parts of SA, had a significant flooding event, affecting several rivers. Winter 1909 was the third-wettest on record for Victoria. The summer of 1910–11 was also particularly wet through most of eastern Australia. From early to mid-1911, the continent began to dry, marking the beginning of the 1911–1916 drought, which affected most of Australia.

Figure 1. May 1909 to Apr 1911
Figure 2. Aug 1909

La Niña: 1906–07

SOI: Weak to Moderate


This La Niña had a moderate but relatively short-lived effect, with above-average rainfalls largely confined to the period August 1906 to January 1907. The three months August–October 1906 (Figure 1) were especially wet, with large areas recording decile 10 totals including record-high falls through western parts of Queensland and NSW, as well as over the north of the NT and northwest WA (although in the latter case totals were modest). Average to above-average falls continued for another three months such that the six months from August 1906 to January 1907 (Figure 2) saw above to very-much-above-average totals over most of eastern and northern Australia. February 1907 effectively marked the end of the event. A neutral SOI pattern became established, with the period from February to April 1907 (Figure 3) being rather dry by comparison: large areas of eastern Australia had falls in deciles 2 or 3 while above-average totals were confined to small patches.

Figure 1. Aug 1906 to Oct 1906
Figure 2. Aug 1906 to Jan 1907
Figure 3. Feb 1907 to Apr 1907

El Niño: 1905–06

SOI: Strong


Despite very strongly negative SOI values in autumn, it wasn't until winter 1905 that drier than average areas began to emerge in eastern Australia. The effect was relatively short-lived with a moderate impact over the 8 months from June 1905 to January 1906 (Figure 1). During this period most parts of eastern and northern Australia recorded below average rainfall, with decile 1 areas scattered throughout. Below average falls also occurred across much of SA and the west of WA.

The driest period during the event over eastern and southern Australia was from November to January, but the pattern changed in February with above average to record falls occurring over southern Queensland and western NSW. High totals were widespread in the east of the country in March, although the monsoon remained weak over the far north. There was a brief return to widespread dry conditions in April.

Figure 1. Jun 1905 - Jan 1906

La Niña: 1903–04

SOI: Moderate


This La Niña followed the Federation drought (1895–1902). Over the 12 months from March 1903–February 1904 (Figure 1) this episode had a moderate to strong effect, with above-average falls over southern and central Australia, Victoria and coastal Queensland. South Australia and the Northern Territory both had over 95% of their areas in the top 3 rain deciles. November 1903–January 1904 (Figure 2) was particularly wet in the north, with parts of the Northern Territory having highest-on-record falls. The return to drier conditions occurred in winter 1904 (Figure 3) with parts of the far north eastern coast of Queensland having their driest winter on record.

Figure 1. Mar 1903 to Feb 1904
Figure 2. Nov 1903 to Jan 1904
Figure 3. Jun 1904 to Aug 1904

El Niño: 1902–03

SOI: Weak


This was the culmination of the Federation Drought with a very strong impact over the eastern half of the country where most rainfall totals for the 12 months from November 1901 to October 1902 (Figure 1) were in the lowest 10% of records. Vast areas of Queensland, NSW and central Australia had record low falls. The southwest of WA was also drier than average.

Negative SOI values occurred from September to December 1901, but apart from February 1902, the next negative monthly SOI value wasn't observed until August 1902. So it was an odd event in this respect.

Areas of above average rainfall were observed in November 1902 over parts of SA, southern NT, western Queensland and the far northwest of NSW heralding further widespread falls in December across southern and eastern Australia. The relief was shortlived though with more dry conditions in January and February 1903. It wasn't until March 1903 that a consistent pattern of above average falls was established.

Figure 1. Nov 1901 to Oct 1902