Sydney in winter 2015: Average rainfall and cool midwinter nights

Sydney recorded close to average rainfall during winter, with two major rain events in mid-June and mid-August. While temperatures were above average at Observatory Hill, a prolonged period of cold nights during July was associated with two snow events in the Blue Mountains and the most cold nights for Sydney since winter 2002.

  • Close to average rainfall
  • Most nights below 8 °C since winter 2002
  • Snow in the Blue Mountains

The Sydney basin recorded average to below average rainfall during winter 2015, with total rainfall at Observatory Hill 26% below the historical average. While 24 days recorded at least 1 mm of rainfall (close to the historical average), only four days had more than 10 mm of rainfall at Observatory Hill. This is well below the historical average of 8 wet days, and the fewest since winter 2005. The heaviest rain was associated with a low pressure system and trough during mid-June, with 67 mm of rain at Observatory Hill and 78 mm at Centennial Park on 19 June. Thunderstorms also produced totals of 54.4 mm at Observatory Hill on 25 August, of which 22.2 mm fell in just 11 minutes on the evening of the 24th, with hail reported in numerous suburbs. This produced flash flooding in some areas, while heavy rainfall to the south of the city contributed to minor flooding in the Hawkesbury-Nepean River.

Temperatures were above average at Observatory Hill and Sydney Airport, with average to below average temperatures recorded at shorter-record stations around the city. Temperatures were coolest during July, when Observatory Hill recorded its coolest mean minimum temperatures since 2002 and the longest spell of cold nights since 1989. This cold spell was associated with two snowfall events in the Blue Mountains, with depths of up to 20 cm recorded on 17 July, the heaviest snowfall since October 2012. For the season as a whole, there were 30 nights that fell to 8 °C or lower at Observatory Hill, the most cold nights since winter 2002.

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Extremes in winter 2015
Hottest day 28.9 °C at Sydney Airport AMO on 22 Aug
Warmest days on average 18.5 °C at Sydney (Observatory Hill)
Coolest days on average 16.4 °C at Springwood (Valley Heights)
Coldest day 10.2 °C at Campbelltown (Mount Annan) on 16 Jul
Coldest night -2.6 °C at Camden Airport AWS on 6 Jul
Coolest nights on average 3.4 °C at Camden Airport AWS
Warmest nights on average 9.2 °C at Sydney (Observatory Hill)
Warmest night 15.4 °C at Sydney (Observatory Hill) on 23 Aug
Warmest on average overall 13.9 °C at Sydney (Observatory Hill)
Coolest on average overall 10.6 °C at Camden Airport AWS
Wettest overall 297.8 mm at Rose Bay (Royal Sydney Golf Club))
Driest overall 106.6 mm at Richmond RAAF
Wettest day 78.0 mm at Centennial Park on 19 Jun
Strongest wind gust 80 km/h at Sydney Airport AMO on 12 Aug

Summary statistics for winter 2015
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean for
winter
2015
Diff
from
average
Highest for
winter
2015
Mean for
winter
2015
Diff
from
average
Lowest for
winter
2015
Total for
winter
2015
Average
for
winter
Rank of
winter
2015
Fraction of
winter
average
Badgerys Creek AWS 17.5 -0.6 28.1 22 Aug 4.8 0.0 -1.3 6 Jul 144.6 112.8 average 128%
Bankstown Airport AWS 18.2 +0.2 28.1 22 Aug 5.9 -0.1 0.6 4 Jul 153.2 169.8 average 90%
Camden Airport AWS 17.8 -0.2 27.3 22 Aug 3.4 -0.4 -2.6 6 Jul 128.4 143.3 average 90%
Campbelltown (Mount Annan) 17.7   27.2 22 Aug 4.3   -1.6 4 Jul 137.2
Canterbury Racecourse AWS 17.6 -0.6 27.6 22 Aug 5.8 -0.7 0.2 15 Jul 197.2 222.2 average 89%
Holsworthy Aerodrome AWS 17.7   27.8 22 Aug 5.6   -0.5 4 Jul 148.8
Horsley Park Equestrian Centre AWS 17.6 -0.4 27.7 22 Aug 5.9 -0.6 -0.2 5 Aug 148.6 142.2 average 105%
Parramatta North (Masons Drive) 18.0 -0.1 27.2 22 Aug 6.6 -0.4 1.8 4 Jul 137.4 188.6 average 73%
Penrith Lakes AWS 18.2 -0.4 28.4 22 Aug 5.7 -0.5 0.0 5 Aug 140.8 112.7 high 125%
Prospect Reservoir 17.7 0.0 27.7 22 Aug 6.4 -0.4 1.3 4 Jul 140.1 181.7 average 77%
Richmond RAAF 18.1 -0.3 28.0 22 Aug 4.4 0.0 -2.5 6 Jul 106.6 109.1 average 98%
Springwood (Valley Heights) 16.4   27.0 22 Aug 6.7   1.5 15 Jul 128.4 186.8 average 69%
Sydney (Observatory Hill) 18.5 +1.5 28.3 22 Aug 9.2 +0.4 5.0 5 Aug 229.4 310.4 average 74%
Sydney Airport AMO 18.4 +0.7 28.9 22 Aug 9.1 +1.1 5.0 4 Jul 199.4 268.8 average 74%
Terrey Hills AWS 16.7 0.0 26.0 22 Aug 7.8 -0.5 1.5 5 Aug 140.4 250.2 low 56%

Notes

The Seasonal climate summary lists the main features of the weather in 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.

A climate summary is generally published on the first working day of each month.

This statement has been prepared based on information available at 9 am on Tuesday 1 September 2015. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

Averages for individual sites 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 10 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.

The ACORN-SAT dataset is used for temperature area averages.

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