Sydney in 2012: Average conditions hide a year of two halves

  • Average rainfall, but wettest single day since 2007.
  • Above average temperatures for 20th consecutive year.
  • Warm days across the city; cool nights in western Sydney

Rainfall - Wet start, dry finish

Sydney Observatory Hill recorded 1213.6 mm of rain during 2012, close to the historical average of 1215 mm. The rain fell over 142 rain days, close to the historical average (144 days), of which twelve recorded at least 25 mm (average for Sydney).

Most of the rain fell during the first part of the year, with 988 mm of rain recorded between January and June, well above the average of 728.7 mm. This was the wettest start to a year since 1990, with particularly heavy falls during March and June. The wet start to the year was associated with the 2011–12 La Niña event, as well as two East Coast Low (ECL) events that brought heavy rain to the city.

On 8 March, a short-lived ECL produced 109.4 mm at Observatory Hill, the wettest single day in Sydney since 2007. Most of the rain fell during the morning peak hour, with 42.4 mm at Observatory Hill between 7:30 and 8:30 am, triggering widespread flash flooding. Two-day totals of 104.8 mm were recorded at Observatory Hill on 19 April, reaching 177.8 mm at Turramurra, resulting in further flash flooding. Finally, an ECL off the north coast produced a 48-hour total of 125.8 mm at Observatory Hill on 12 June, reaching 176.6 mm at Dover Heights in eastern Sydney.

The second half of the year was generally dry across the city, with only 225.6 mm recorded between July and December (average 487 mm). This was the driest such period for Sydney since 2002 and the eleventh-driest end to a year since records began in 1858, associated with generally above-average pressure and a lack of cold fronts. There were no days above 25 mm recorded during this period, only the eighth such time on record, with only seven days recording at least 10 mm (average 13 days).

Sydney's water storage is currently at 89.0 percent of capacity. This is 9 percent higher than at the start of 2012 (80.5%) and 17 percent higher than in early 2011 (72.5 %). Current water storage information can be found on the Bureau of Meteorology Water Storage web site.

Temperature - 20th consecutive warm year

The average daily temperature at Sydney Observatory Hill was 0.8 °C above average during 2012, with temperatures closer to normal at shorter-record stations in western Sydney. This was the 20th consecutive year with above-average temperatures in Sydney, with both days and nights warmer than average in the city, while nights were cooler than average in western Sydney.

Sydney Observatory Hill recorded an average maximum temperature of 22.7 °C, 1.0 °C above the historical average and the warmest year since 2009. Temperatures were coolest at the start of the year, with above-average rainfall and cloudiness resulting in close to normal daytime temperatures, the coolest January–March since 2008. Days were generally warmer than average for the rest of the year, with temperatures averaging 1.4 °C above average during both winter and spring. Temperatures were particularly warm during September, which was the eighth-warmest for Sydney since records began in 1859.

There were fourteen days above 30 °C during the year, close to the historical average of 15 days but the fewest since 2007. This reflects a very cool start to the year, with only two days above 30 °C in summer 2011–12 but seven during spring, double the historical average (4 days). Only seven days were cooler than 15 °C during 2012, the fewest since 2009 (average 25 days), with a particular lack of cool days during spring.

Sydney Observatory Hill recorded an average minimum temperature of 14.4 °C, 0.6 °C above the historical average. Nights were generally within 1 °C of normal throughout the year, with warmest conditions in January and September and coolest nights in May. No nights dropped below 5 °C during the year (average 3 nights), with the coolest night reaching 5.5 °C on 1 September.

In western Sydney, Richmond RAAF experienced close to normal night-time temperatures in the first half of the year, with the exception of very cool conditions during May, the fourth-coolest on record for Richmond. Nights cooled later in the year, with minimums more than 1.5 °C below average between August and October, the third-coolest such period since records began in 1929 due to prevailing clear, dry conditions. Fourteen nights dropped below 0 °C at Richmond, close to the historical average, with the coldest night reaching –2.4 °C on 8 August.

Other phenomena

Sydney Airport recorded an average of 7.3 hours of bright sunshine during 2012, slightly above the historical average (7.2 hous) and the sunniest year since 2009, with particularly sunny conditions during May and early spring. There were 23 days with thunderstorms at Sydney Airport, slightly above the historical average and significantly higher than 2011 (12 storms), with 46 days reporting storms anywhere in the metropolitan area. There were 74 strong wind days reported at the airport, with gusts reaching at least 100 km/hr on two days, the most since 2003.

On 5 June, an East Coast Low moved rapidly up the coast, with gusts reaching 104 km/h at the airport and 117 km/h at Port Botany. Sustained winds remained above 50 km/h for more than 12 hours overnight, the most sustained strong winds since the ECL of June 2007, with maximum wave heights off Sydney exceeding 10 m for eighteen hours. The combination of this event and heavy rainfall across NSW between 27 February and 4 March resulted in Warragamba Dam reaching full capacity for the first time since 1998, with overflows leading to minor flooding in western Sydney.

Wind gusts again reached 106 km/h at the airport and 115 km/h at Port Botany associated with an offshore low on 10 August, with wind speeds remaining above 50 km/h for almost twelve hours and 10-minute mean wind speeds as high as 80 km/h. Finally, wind gusts reached 107 km/h at Penrith during a localised severe thunderstorm on 8 November.

Further information

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Extremes in 2012
Hottest day 39.7 °C at Badgerys Creek AWS on 24 Dec
Warmest days on average 24.1 °C at Penrith Lakes AWS
Coolest days on average 21.4 °C at Terrey Hills AWS
Coldest day 10.7 °C at Springwood (Valley Heights) on 26 Jun
Coldest night -2.8 °C at Camden Airport AWS on 8 Aug
Coolest nights on average 9.7 °C at Camden Airport AWS
Warmest nights on average 14.4 °C at Sydney (Observatory Hill)
Warmest night 25.3 °C at Sydney (Observatory Hill) on 31 Jan
Warmest on average overall 18.6 °C at Sydney Airport AMO
Coolest on average overall 16.6 °C at Camden Airport AWS
Wettest overall 1410.1 mm at Turramurra (Kissing Point Road)
Wettest day 134.4 mm at Lucas Heights (ANSTO) on 8 Mar
Highest wind gust 117 km/h at Port Botany (Molineux Point AWS) on 5 Jun

Summary statistics for 2012
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean
for
2012
Diff
from
average
Highest
for
2012
Mean
for
2012
Diff
from
average
Lowest
for
2012
Total
for
2012
Average
annual
total
Rank
of
2012
Fraction
of annual
average
Badgerys Creek AWS 23.4   39.7 24 Dec 10.4   -1.1 8 Aug 903.4
Bankstown Airport AWS 23.4 +0.2 39.1 30 Nov 11.7 -0.3 0.6 4 Aug 917.0 875.3 average 105%
Camden Airport AWS 23.4 -0.2 39.4 24 Dec 9.7 -0.5 -2.8 8 Aug 796.8 788.1 average 101%
Campbelltown (Mount Annan) 23.3   38.2 24 Dec 9.9   -1.2 8 Aug 776.6
Canterbury Racecourse AWS 22.5   36.0 1 Dec 11.8   0.4 8 Aug 1019.0
Holsworthy Control Range 22.9   37.7 30 Nov 10.7   -0.7 5 Aug 881.8
Horsley Park Equestrian Centre AWS 23.1   38.6 24 Dec 11.4   0.1 7 Aug 973.8
Parramatta North (Masons Drive) 23.0 -0.3 39.3 30 Nov 11.8 -0.4 0.7 1 Sep 1081.8 969.8 high 112%
Penrith Lakes AWS 24.1   38.8 24 Dec 11.8   0.7 8 Aug 905.4
Prospect Reservoir     38.8 30 Nov 12.0 -0.2 1.7 8 Aug 972.9 871.7 average 112%
Richmond RAAF 24.0   38.8 24 Dec 10.5   -2.4 8 Aug 824.2
Springwood (Valley Heights) 22.0   37.0 24 Dec 11.6   2.2 7 Aug 1007.7 1089.9 average 92%
Sydney (Observatory Hill) 22.7 +1.0 34.2 5 Oct 14.4 +0.6 5.5 1 Sep 1213.6 1215.0 average 100%
Sydney Airport AMO 22.9 +0.7 36.2 1 Dec 14.3 +0.9 5.1 1 Sep 972.8 1082.8 average 90%
Terrey Hills AWS 21.4   34.0 28 Dec 12.8   3.4 24 Jun 1277.2

Notes

A Annual Climate Summary is prepared to list the main features of the weather in Sydney - Greater Sydney using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.

This statement has been prepared based on information available at 9 am on Wednesday 2 January 2013. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

Averages are long-term means based on observations from all available years of record, which vary widely from site to site. They are not shown for sites with less than 20 years of record, as they cannot then be calculated reliably.
The median is sometimes more representative than the mean of long-term average rain.

The Rank indicates how rainfall this time compares with the climate record for the site, based on the decile ranking (very low rainfall is in decile 1, low in decile 2 or 3, average in decile 4 to 7, high in decile 8 or 9 and very high is in decile 10).
The Fraction of average shows how much rain has fallen this time as a percentage of the long-term mean.

Further information

Media
(03) 9669 4057
Enquiries