Sydney in autumn 2012: A season of rainfall extremes

  • Above average rainfall across the city
  • Wettest day since 2007; longest dry spell since 2002.
  • Close to average temperatures

Rainfall

Sydney Observatory Hill recorded 455.2 mm of rain during autumn, above the historical average of 376.8 mm but drier than autumn 2011 (533.4 mm), with falls above average across the city. Most of the rain fell during March, which was the wettest since 1984, with totals closer to average during April and well below average during May. The rain fell over 30 rain days, below the historical average of 39 days and the fewest since 2007.

There were several rain events during the season, with falls reaching 109.4 mm at Observatory Hill and up to 134 mm at Lucas Heights during an East Coast Low on the 8th, the wettest single day for Sydney since 2007, causing flash flooding in the city. Further flash flooding was recorded in mid-April, with a 48-hour total of at least 104.8 mm at Observatory Hill to 9am on the 19th, and 2-day totals as high as 177.8 mm at Turramurra in northern Sydney. In contrast, Sydney Observatory Hill had 25 consecutive dry days between April 26 and May 20, the longest dry spell since 2002.

Temperature

The average maximum temperature at Sydney Observatory Hill during autumn was 23.1 °C, 0.9 °C above the historical average. Temperatures were generally warm during April and May, associated with dry, sunny conditions, while rainy conditions drove cooler days across the city during March.

Days were particularly warm in early April, with seven consecutive days above 25 °C for only the third time on record, while temperatures reached 29.1 °C on May 10th, the 4th warmest May day on record. While no days exceeded 30 °C during the season (average 2 days), only fifteen dropped below 20 °C (average 26), with temperatures consequently mild throughout the season.

The average minimum temperature at Sydney Observatory Hill was 14.8 °C, 0.2 °C above the historical average, while nights were generally cool throughout the city. Nights were coldest during May when conditions were clear, particularly in western Sydney, with closer to average nights during March and April. The average temperature for Sydney was consequently 18.9 °C, 0.5 °C above the historical average.

Wind

The prevailing winds at Sydney Airport were generally NW-S during the mornings, 83% of 9am winds, and S-NE during the afternoons (73%), normal for autumn. There were 18 strong wind days during autumn, the most since 18 days in autumn 2003, with a maximum wind gust of 74 km/hr on April 24.

Other phenomena

Sydney Airport recorded an average of 7.2 hours of bright sunshine during autumn, above the historical average of 6.7 hours. Seven thunderstorms were reported at the airport (average 3-4 storms), with eight reported anywhere in the Metropolitan region.

Further information

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Extremes in autumn 2012
Hottest day 32.8 °C at Richmond RAAF on 16 Mar
Warmest days on average 23.6 °C at Penrith Lakes AWS
23.6 °C at Richmond RAAF
Coolest days on average 21.5 °C at Terrey Hills AWS
Coldest day 12.6 °C at Badgerys Creek AWS on 24 May
Coldest night -0.2 °C at Camden Airport AWS on 24 May
Coolest nights on average 10.2 °C at Camden Airport AWS
Warmest nights on average 14.8 °C at Sydney (Observatory Hill)
14.8 °C at Sydney Airport AMO
Warmest night 20.4 °C at Sydney Airport AMO on 15 Mar
Warmest on average overall 18.9 °C at Sydney (Observatory Hill)
18.9 °C at Sydney Airport AMO
Coolest on average overall 16.6 °C at Camden Airport AWS
Wettest overall 500.0 mm at Castle Cove (Rosebridge Ave)
Wettest day 134.4 mm at Lucas Heights (ANSTO) on 8 Mar
Highest wind gust 94 km/h at Port Botany (Molineux Point AWS) on 1 Mar

Summary statistics for autumn 2012
Maximum temperatures
for autumn
(°C)
Minimum temperatures
for autumn
(°C)
Rainfall
for autumn
(millimetres)
Mean for
autumn
2012
Diff
from
average
Highest for
autumn
2012
Mean for
autumn
2012
Diff
from
average
Lowest for
autumn
2012
Total for
autumn
2012
Average
for
autumn
Rank of
autumn
2012
Fraction of
autumn
average
Badgerys Creek AWS 23.0   29.6 16 Mar 10.9   1.0 23 May 340.4
Bankstown Airport AWS 23.3 -0.1 31.2 16 Mar 12.2 -0.6 3.0 23 May 385.4 255.0 high 151%
Camden Airport AWS 22.9 -0.8 30.8 16 Mar 10.2 -0.7 -0.2 24 May 327.0 212.1 high 154%
Campbelltown (Mount Annan) 23.0   30.8 16 Mar 10.5   1.1 23 May 329.8
Canterbury Racecourse AWS 22.8   30.5 16 Mar 12.1   3.0 23 May 398.8
Holsworthy Control Range 22.7   31.0 16 Mar 11.3   0.8 23 May 368.4
Horsley Park Equestrian Centre AWS 22.8   31.4 16 Mar 12.0   4.6 13 May 369.8
Parramatta North (Masons Drive) 22.9 -0.6 31.2 16 Mar 12.1 -0.8 4.0 14 May 404.2 271.6 high 149%
Penrith Lakes AWS 23.6   31.1 16 Mar 12.4   3.5 23 May 258.2
Prospect Reservoir 22.9 -0.5 30.1 4 Mar 12.4 -0.6 5.5 15 May 354.1 242.6 high 146%
Richmond RAAF 23.6   32.8 16 Mar 11.2   0.6 14 May 281.0
Riverview Observatory 22.9 +0.4 29.8 1 Mar 12.7 -0.3 7.0 24 May 429.2 341.2 high 126%
Springwood (Valley Heights) 21.7   28.7 16 Mar 12.0   5.5 14 May 356.4 288.8 high 123%
Sydney (Observatory Hill) 23.1 +0.9 29.5 1 Mar 14.8 +0.2 8.5 15 May 455.2 377.3 average 121%
Sydney Airport AMO 23.0 +0.3 31.3 16 Mar 14.8 +0.6 8.6 15 May 349.2 322.7 average 108%
Terrey Hills AWS 21.5   29.3 1 Mar 13.3   6.9 15 May 468.0

Notes

A Seasonal 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 11 am on Friday 1 June 2012. 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