30  July 2021 — Financial year summary for Australia — Product Code IDCKGC6AR0

Australia in the 2020 to 2021 financial year

Highlights

• The 2020–21 financial year (July 2020 to June 2021) was the coolest and wettest for Australia since 2016–17, after three exceptionally warm and dry years.
• The Australian average mean temperature was 0.83 °C above the 1961–90 climatological averaging period, just outside the 10 warmest financial years since national records began in 1910.
• The Australian average total rainfall was 10% above the 1961–90 climatological averaging period, at 515.2 mm.
• A weak La Niña influenced Australian climate, this contributed to the third-wettest December on record and the wettest northern wet season (October to April) since 2016–17.
• Improved rainfall conditions resulted in average to above average annual streamflows across large parts of the country, particularly in northern Australia and coastal catchments in the south-east.
• Although water storage levels improved compared to 2019–20 in many parts of the country groundwater levels were mostly below average.
• A total of 8 tropical cyclones were observed across the Australian region, slightly less than the average since 2000 of 9 per financial year; three tropical cyclones reached severe (category 3) strength.
• Extreme rainfall totals caused significant flooding along the New South Wales coast in March 2021 and in the Gippsland region of Victoria in June 2021.

Rainfall slightly above average

The Australian total rainfall for the 2020–21 financial year (July 2020 to June 2021) was 10% above average, a significant change from the preceding three drier-than-average financial years (see Figure 1, Figure 2, and Table 1), including 2019–20 and 2018–19 which were the third- and fourth-driest financial years since national records began in 1900.

December 2020 was Australia's third-wettest December on record, owing to a number of tropical lows affecting the north-west of the country and a slow-moving low pressure system on the east coast. March 2021 was also very wet, with rainfall for New South Wales more than double the March average, and the second-wettest March on record for the state.

Rainfall during April 2021 was very low for the south-eastern mainland. For New South Wales it was the ninth-driest April on record and for South Australia it was the seventh-driest.

A dry 2019–2020 saw the financial year start with below average soil moisture over much of the country (Figure 3a). Wetter conditions from August saw significant change in soil moisture by the end of the year with root-zone soil moisture for December 2020 (Figure 3b) very much above average for large areas of the north-west and the Northern Territory.

Despite a very dry April, by June 2021 soil moisture was close to average across large areas of the country (Figure 3c).

A warmer than average 12 months

For the 2020–21 financial year, Australia was cooler than the preceding three financial years, which were each amongst the five warmest financial years since national records began in 1910 (Figure 4 and Figure 5). 2020–21 was just outside the 10 warmest financial years on record, with the mean temperature anomaly 0.83 °C above the 1961–90 average.

Both daytime and night-time temperatures were warmer than average, with Australia's mean maximum temperature 0.89 °C warmer than average, and the mean minimum temperature 0.76 °C warmer than average, and the ninth-highest on record (Table 2).

Warmth was widespread and persistent throughout the early part of 2020–21, with the Australian mean temperature amongst the ten warmest on record for August, September, and November 2020. Both November and spring as a whole were warmest on record.

Water resources

Improved rainfall conditions across much of Australia in 2020–21 increase the water in the soil, storages, rivers, and groundwater. Heavy rainfall in March 2021 resulted in some recovery of water resources in the drought affected areas of the northern Murray–Darling Basin but also caused major flooding in catchments along the south-east coast.

Mostly above average streamflows

Higher rainfall in 2020–21 than in the three previous financial years contributed to generally average to above average streamflow across many parts of the country (Figure 6). In the Murray–Darling Basin (MDB), above average rainfall during spring 2020, built on the earlier high rainfall in February–April 2020, resulting in generally average streamflow conditions throughout the latter half of 2020. High rainfall across the entire northern MDB in late March 2021 resulted in well above average river flows, including highest-on-record flows in catchments near the New South Wales–Queensland border. Throughout April–May 2021, floodwaters from the March rainfall made their way downstream to fill the Menindee Lakes system to its highest level in four years (see the Drought Statement for May 2021 for more information).

The heavy rainfall in late March 2021 in eastern New South Wales, south-eastern Queensland and large inland areas across both states, resulted in significant coastal and inland riverine flooding Some areas experienced their worst floods in more than 30 years (see Special Climate Statement 74 for more information). The high flows during this event contributed to the well above average annual streamflows in many catchments along Australia's south-east coast.

Average to above average flows also occurred across most of northern Australia following two consecutive years of very low flows in most of the region's major rivers. The streamflow in south-west Western Australia was below average in 2020–21 for the second consecutive year due to below average winter rainfall. Streamflow in many of the mid-coast catchments in Queensland was also below average.

Increasing surface water availability

Storage volumes at the end of June 2021 were higher than at the same time in 2020 for the majority of the water storages (Figure 7). However many remained below 30% full at the end of the financial year (Figure 8).

In south-eastern Australia generally wetter conditions during the financial year resulted in improvements in storage levels throughout most of the MDB with the total accessible storage volume at 65% full on 30 June 2021, 21% higher than at the same time in 2020.

The volume of water in all storages across the northern MDB increased following heavy rainfall during the second half of March 2021 (Figure 9). The total storage in the southern MDB increased to 67.3% which is significantly higher than the storage situation at the same time last financial year when it was only 49.7%.

The volume of water in major water storages in northern Australia increased significantly during the northern wet season (November to April) due to the above average rainfall in northern parts of the Northern Territory and north-eastern Western Australia from December to April. Water levels in Lake Argyle, the largest water supply storage in Australia, was at 25% of accessible capacity at the end of November 2020, the lowest level in almost 30 years (Figure 10) due to poor wet season rainfall for three consecutive years, butrose to 82.1% of accessible capacity at the end of March 2021. With the end of the northern wet season the storage volume has decreased to 75.5% capacity at the end of June.

Storages in south-east Queensland were very low in June 2021. The largest storage in the region, Wivenhoe, had dropped to its lowest level (36%) in more than 10 years during March 2021 (Figure 11). By the end of June 2021, the storage was only 41.6%, significantly lower than the 48.4% storage at the same time in 2020.

Low groundwater levels but some signs of recovery

While surface water generally increased during 2020–21, groundwater levels generally remained below average during the financial year. This was due to reduced or no recharge, and increased pumping of groundwater due to the prolonged drought conditions since 2017 (Figure 12).

Regionally, severe rainfall deficiencies in south-east Queensland in 2020–21 and south-west Western Australia in early 2020–21 further reduced groundwater levels in these areas. In contrast, groundwater levels were above average in north-east Queensland and the Top End of the Northern Territory due to high rainfall driven by La Niña conditions and a good wet season.

The drought conditions from 2017 to March 2021 also resulted in a widespread decline in groundwater levels in the MDB during 2020–21, though in late 2020–21 levels started to recover due to heavy rainfall in late March and the usual end of the pumping season (Figure 13).

Groundwater levels also showed signs of recovery in the Gnangara Mound near Perth due to above average rainfall in the second half of 2020–21 (Figure 13). Prior to this, the Perth region experienced two consecutive years of low winter rainfall resulting in low groundwater recharge and low groundwater levels.

Major climate influences

A weak La Niña influenced Australian climate during the 2020–21 financial year. Early indications of a developing La Niña emerged in the tropical Pacific region in June 2020. La Niña development continued, with an event announced by the Bureau in late September. La Niña conditions in the tropical Pacific persisted through summer 2020–21, with a neutral El Niño-Southern Oscillation (ENSO) state returning during March 2021.

La Niña typically brings above average rainfall to much of northern and eastern Australia during winter, spring and into the summer months. The 2020–21 La Niña was one of the key drivers of wetter spring and summer conditions for large parts of Australia, though atypically, areas of south-east to central coast Queensland experienced below average rainfall.

The Southern Annular Mode (SAM) was mostly in a positive phase from the months of October 2020 to February 2021, and slightly weaker in November 2020. La Niña tends to favour positive SAM during late spring and early summer months. Additionally, the polar vortex over Antarctica was the strongest on record during late spring 2020, further strengthening the positive SAM.

A positive SAM during late spring and early summer typically enhances the wet signal of La Niña in parts of eastern Australia, although western Tasmania is typically drier as the westerly rain-bearing winds are suppressed. June 2021 saw a return to a positive SAM to end the 2020–21 financial year.

During July and August 2020 much of the northern and eastern regions of the Indian Ocean basin, including waters to the north-west of Australia, were warmer than average. The Indian Ocean Dipole (IOD) exceeded negative IOD thresholds for a number of weeks during late winter and early spring, but these values were not sustained for long enough (a minimum of eight weeks) to be considered an official IOD event. However, it is likely that the warm sea surface temperatures in the eastern Indian Ocean contributed to above average rainfall over Australia between August and October.

In late May 2021, a negative IOD pattern reappeared, with the final six weeks of the 2020–21 financial year below negative IOD thresholds. This pattern likely contributed to the above average rainfall observed across much of Australia during June 2021.

In addition to the influence of natural climate drivers, Australia's climate is increasingly influenced by global warming. Australia's climate has warmed on average by 1.44 ± 0.24 °C since national records began in 1910, with most of the warming occurring since 1950. The ocean waters around Australia have also warmed over the past century, contributing to the large area of very much above average (decile 10, the warmest 10% of all years since 1900) ocean temperatures in the Australia region in the 2020–21 financial year (Figure 14).

There has also been a significant decline in autumn and winter rainfall observed over south-east and south-west Australia in recent decades. The drying trend is particularly strong for May to July over south-west Western Australia since 1970, and for April to October over the south-east of the continent since 1999. Rainfall across northern Australia has increased during the northern wet season (October to April) since the 1970s, with more high intensity and short duration rain events. The role of climate change is further discussed in the State of the Climate report.

Significant events

In July 2020, a low pressure system created a powerful sea swell with wave heights of 5 to 6 m, leading to significant coastal erosion and hazardous beach conditions on the New South Wales coast. Powerful waves persisted for several days, with peak waves exceeding 11.5 m recorded offshore of Sydney.

A complex low pressure system and cold front crossing southern Australia brought heavy rainfall and a significant cold outbreak to the south-east of the country during the first week of August. Widespread heavy snow fell on 4 August in the Victorian Alpine region, and settled at lower levels, including at Mount Macedon, the Otway Ranges, Dandenong Ranges, Wallan and Sunbury in Victoria. In Tasmania snow closed the Huon Highway south of Hobart, and in a rare occurrence a few cm settled on the ground in Launceston. Liawenee set a record for the lowest temperature observed in Tasmania with −14.2 °C on 7 August (Table 3).

Severe thunderstorms affected much of south-east Queensland on 31 October, with giant hail up to 14 cm in diameter reported at Forestdale and hail up to 13 cm in diameter reported at Hillcrest, both suburbs of Brisbane. These hailstones were amongst the largest ever measured in Australia.

On 28 and 29 November 2020 severe to extreme heatwave conditions occurred in the west and north-east of New South Wales, extending to the Sydney region. In the north-west of the state, Smithville reported 46.9 °C on 28 November, the highest November temperature recorded in New South Wales. On 29 November many sites had their warmest November night on record including Delta, west of Bourke, with 33.8 °C (Table 3) the highest November minimum temperature ever recorded in New South Wales, and the fourth-highest for all of Australia.

In December, a slow-moving low pressure system and trough near the southern Queensland coast brought widespread heavy rainfall, damaging winds, abnormally high tides and dangerous surf to the northern half of the New South Wales coast and south-east Queensland from 12 to 17 December. Upper Springbrook Alert recorded 918 mm over 13 to 15 December. Flash and riverine flooding occurred in Gold Coast hinterland in south-east Queensland, and in the Tweed, Clarence, Richmond/Wilsons and Bellinger rivers in New South Wales. Damaging storm surges coincided with king tides, resulting in major coastal erosion at numerous beaches in north-east New South Wales and south-east Queensland.

A major rain event affected many parts of eastern and central Australia in the second half of March. The highest rainfall totals occurred in coastal New South Wales, with the week ending 24 March 2021 the wettest week for the region since national daily records began in 1900. Extensive heavy rainfall also occurred over large areas inland, particularly much of inland New South Wales and northern South Australia. Many catchments on the east coast experienced significant flooding, as did numerous inland rivers. For more details see Special Climate Statement 74: Extreme rainfall and flooding in eastern and central Australia in March 2021.

A tropical low that formed well off the north-west of Australia was named Seroja on 5 April. The system quickly intensified into a category 2 tropical cyclone. During 8 and 9 April it interacted with another tropical low, that briefly intensified into tropical cyclone Odette, in a rare process called the Fujiwara effect. Tropical cyclone Seroja intensified into a severe (category 3) tropical cyclone on 11 April and maintained this intensity through to its coastal crossing just south of Kalbarri that evening. It is very unusual for severe tropical cyclones to maintain their intensity this far south.

A total of 8 tropical cyclones were observed across the Australian region during the 2020–21 financial year. This is less than the long-term average of 11 and the post-2000 average of 9 per season. Three of the 8 tropical cyclones were rated as severe. Four tropical cyclones were observed in the Western region, three in the Eastern region. For the first time since 2015–16, there were no tropical cyclones observed in the waters of the Northern Territory.

On 9 June, a complex low produced heavy rainfall and damaging winds across Victoria that did significant damage in some regions and cut power to more than 200,000 people. Major flooding occurred in multiple West Gippsland catchments after more than 200 mm of rain fell in 24 hours on 10 June.

Tables

More information

For more information, see area average data and time series for the financial year period, with maps for the 12-months periods ending June available from recent conditions. This current and historical climate information allows for comparison of climate impacts from one year to the next, and aligns with other reporting processes that occur over financial year periods.