Greater Sydney in summer 2017-18: Another hot and dry summer

Summer 2017-18 was warmer than average, with several heatwave events experienced during December and January. Several monthly and summer records were set for single hottest days and warmest days overall, especially in the west of Greater Sydney. Overnight temperatures were also warmer than average over summer, with December being particularly warm. Rainfall was below average across the region, with fewer than average significant events. Late season rainfall brought some relief to the region.

Dry across Greater Sydney

  • Rainfall was below average across the region; January was particularly dry, with December and February receiving closer to average rainfall
  • Total rainfall for Sydney (Observatory Hill) was 197.8 mm, which is 67% of the long-term average of 296.7 mm
  • The southwest of Greater Sydney was more affected by the drier conditions, with many sites in that area only receiving 40% to 50% of their typical summer rainfall
  • The most significant rainfall event of the season occurred during the last week of summer as a cold front and associated low pressure trough moved across Sydney on 25 February bringing widespread rainfall; totals of 50 mm to 90 mm were recorded in the northern half of the region and 30 mm to 50 mm across the south, for the 24 hour period to 9am on 26 February; St Ives recorded 91.2 mm, the wettest day of summer across Greater Sydney
  • Other notable rainfall events occurred at the start of summer when rain and thunderstorms moved through the region on 3 December, producing widespread falls of more than 10mm, with further showers that continued for several days; 8 January also brought showers and thunderstorms to the region with a trough of low pressure that resulted in 43.0 mm being recorded at Mount Wilson over the 24 hours to 9am on 9 January
  • Significant rainfall events were fewer this summer with Sydney (Observatory Hill) only recording four days with 10 mm or more of rain, compared to the average of eight days; similar trends were observed across the region
  • Sydney (Observatory Hill) recorded rain on 38 days over summer, which is close to average for this season; in the southwest, Camden and Bankstown recorded rainfall on 23 days, below their summer averages of 31 and 32 days respectively
  • Sunshine at Sydney Airport was close to average, with around 7.7 hours of hours of bright sunshine on average per day over summer

A summer of records in the west

  • The mean daily maximum temperature for Sydney (Observatory Hill) was 27.6 °C, which is 1.9 °C above the long-term average of 25.7 °C, and the fifth warmest summer on record
  • Mean daily maximum temperatures were much warmer than average across the region, particularly in the west, where Penrith Lakes recorded an average of 33.5 °C, which is 3.6 °C warmer than usual and its warmest ever summer on record, beating the 16/17 summer record; several other sites in the west equaled their warmest ever summer, including Camden, Richmond and Horsley Park
  • Summer 17/18 was characterised by several heatwave events during December and January; a number of sites set records for their hottest December and January days and hottest overall for mean maximum temperatures for both months
  • The heatwave in early January also produced new summer records, with several sites recording their hottest ever summer temperature on record; Penrith Lakes recorded a maximum temperature of 47.3 °C, the hottest on record and also the second hottest day ever recorded in Greater Sydney (below Sydney's all-time record of 47.8 °C at the old Richmond site on 14 January 1939)
  • A record number of hot days 35 °C or higher were experienced in the west, with Penrith Lakes recording 38 days hotter than 35 °C during summer, four more than the previous record of 34 days set last summer, and more than double the typical number of hot days for summer
  • Overnight temperatures were also warmer than average; the mean daily minimum temperature for Sydney (Observatory Hill) was 19.9 °C, which is 1.5 °C above the long-term average of 18.4 °C and the equal eighth warmest on record
  • The start of summer brought particularly warm overnight temperatures with several sites having their highest December mean daily minimum temperatures on record; several records were also set for consecutive number of warm nights of 20 °C or more during December, including Sydney (Observatory Hill)
  • The morning of 20th December was particularly warm with Mangrove Mountain and Horsley Park recording their warmest summer night (highest daily minimum temperature) on record; at 9am on the 20th, Sydney (Observatory Hill) had already reached 35.3 °C, the second-highest 9am temperature on record at the site
  • January and February saw overnight temperatures return to closer to normal, with most sites recording mean daily minimum temperatures within 1 °C of average

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Extremes in summer 2017-18
Hottest day 47.3 °C at Penrith Lakes AWS on 7 Jan 2018
Warmest days on average 33.5 °C at Penrith Lakes AWS
Coolest days on average 24.4 °C at Sydney Harbour (Wedding Cake West)
Coldest day 12.8 °C at Katoomba (Murri St) on 25 Dec 2017
Coldest night 7.2 °C at Mount Boyce AWS on 15 Jan 2018
Coolest nights on average 13.6 °C at Mount Boyce AWS
Warmest nights on average 20.1 °C at Sydney Harbour (Wedding Cake West)
Warmest night 26.2 °C at Mangrove Mountain AWS on 20 Dec 2017
Warmest on average overall 26.1 °C at Penrith Lakes AWS
Coolest on average overall 19.7 °C at Mount Boyce AWS
Wettest overall 429.2 mm at Mount Wilson (Clarine)
Wettest day 91.2 mm at St Ives (Richmond Avenue) on 26 Feb 2018
Strongest wind gust 113 km/h at Wattamolla AWS on 9 Jan 2018



Record highest summer temperature
New record
(°C)
Old
record
Years of
record
Average for
summer
Prospect Reservoir 45.3 on 7 Jan 2018 45.1 on 18 Jan 2013 53 28.0
Canterbury Racecourse AWS 44.9 on 7 Jan 2018 44.6 on 18 Jan 2013 23 27.2
Penrith Lakes AWS 47.3 on 7 Jan 2018 46.9 on 11 Feb 2017 23 29.9
Horsley Park Equestrian Centre AWS 45.6 on 7 Jan 2018 44.9 on 18 Jan 2013 21 28.9



Record highest summer mean daily maximum temperature
New record
(°C)
Old
record
Years of
record
Average for
summer
Camden Airport AWS 31.8 = 31.8 in 2016 41 28.9
Richmond RAAF 32.9 = 32.9 in 2016 24 29.3
Penrith Lakes AWS 33.5 32.8 in 2016 22 29.9
Horsley Park Equestrian Centre AWS 31.5 = 31.5 in 1997 20 28.9



Record highest summer daily minimum temperature
New record
(°C)
Old
record
Years of
record
Average for
summer
Mangrove Mountain AWS 26.2 on 20 Dec 2017 26.1 on 31 Jan 2017 24 16.4
Horsley Park Equestrian Centre AWS 25.0 on 20 Dec 2017 24.8 on 31 Jan 2017 21 17.3



Summary statistics for summer 2017-18
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean for
summer
2017-18
Diff
from
average
Highest for
summer
2017-18
Mean for
summer
2017-18
Diff
from
average
Lowest for
summer
2017-18
Total for
summer
2017-18
Average
for
summer
Rank of
summer
2017-18
Fraction of
summer
average
Badgerys Creek AWS 31.6 +2.6 45.0 7 Jan 2018 17.3 +0.8 10.6 18 Jan 2018 135.8 235.0 low 58%
Bankstown Airport AWS 30.4 +2.5 45.2 7 Jan 2018 18.5 +0.8 12.2 18 Jan 2018 110.0 261.4 v low 42%
Camden Airport AWS 31.8 +2.9 45.7 7 Jan 2018 17.1 +0.8 9.7 18 Jan 2018 113.4 238.3 low 48%
Campbelltown (Mount Annan) 31.5 +2.7 45.1 7 Jan 2018 16.8 +0.5 10.5 18 Jan 2018 112.0 237.1 low 47%
Canterbury Racecourse AWS 28.9 +1.7 44.9 7 Jan 2018 18.4 +0.6 11.9 18 Jan 2018 206.4 243.6 average 85%
Cooranbong (Lake Macquarie AWS) 29.3   43.4 7 Jan 2018 17.0   8.8 18 Jan 2018 173.2 322.4 v low 54%
Gosford AWS 28.4   43.7 7 Jan 2018 18.7   12.3 18 Jan 2018 251.6
Holsworthy Aerodrome AWS 29.9   45.2 7 Jan 2018 17.4   10.5 18 Jan 2018 112.0
Horsley Park Equestrian Centre AWS 31.5 +2.6 45.6 7 Jan 2018 17.7 +0.4 10.5 18 Jan 2018 129.8 246.1 low 53%
Katoomba (Murri St) 25.6 +2.8 36.7 7 Jan 2018 14.2 +1.7 7.7 14 Jan 2018 288.0 455.4 low 63%
Mangrove Mountain AWS 29.3 +2.6 44.0 7 Jan 2018 16.7 +0.3 9.5 18 Jan 2018 290.8 332.7 average 87%
Mount Boyce AWS 25.8 +2.7 37.0 7 Jan 2018 13.6 +0.9 7.2 15 Jan 2018 254.4 324.5 low 78%
Norah Head AWS 27.2 +1.5 34.5 11 Feb 2018 19.7 +0.3 15.3 18 Jan 2018 242.8 259.5 average 94%
Parramatta North (Masons Drive) 30.4 +2.5 45.0 7 Jan 2018 17.5 +0.3 11.0 18 Jan 2018 178.0 302.0 low 59%
Penrith Lakes AWS 33.5 +3.6 47.3 7 Jan 2018 18.6 +0.6 12.4 18 Jan 2018 157.4 273.8 low 57%
Prospect Reservoir     45.3 7 Jan 2018 18.1 +0.8 11.2 18 Jan 2018 170.0 266.4 average 64%
Richmond RAAF 32.9 +3.6 46.3 7 Jan 2018 17.8 +0.6 10.5 18 Jan 2018 138.0 276.1 low 50%
Sydney (Observatory Hill Comparison) 28.4   42.5 7 Jan 2018 19.6   14.5 14 Jan 2018 208.4
Sydney (Observatory Hill) 27.6 +1.9 43.4 7 Jan 2018 19.9 +1.5 14.8 14 Jan 2018 197.8 296.7 average 67%
Sydney Airport AMO 28.8 +2.5 43.7 7 Jan 2018 19.8 +1.3 14.9 14 Jan 2018 168.0 279.5 low 60%
Sydney Harbour (Wedding Cake West) 24.4 0.0 33.2 30 Dec 2017 20.1 +0.2 15.5 14 Jan 2018
Sydney Olympic Park AWS (Archery Centre) 29.6   44.5 7 Jan 2018 18.8   12.6 18 Jan 2018 219.4
Terrey Hills AWS 27.7 +1.7 42.7 7 Jan 2018 18.1 +0.4 13.0 14 Jan 2018

Notes

The Seasonal climate summary, generally published on the first working day of each month, lists the main features of the weather in Greater Sydney using the most timely and accurate information available on the date of publication; it will generally not be updated. More extensive discussion of significant weather events, along with later information and data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review.

In September 2017 this summary was broadened to include data from observing sites in or near the Greater Sydney “Greater Capital City Statistical Area” (GCCSA). The Australian Bureau of Statistics designed the GCCSAs to “include the population within the urban area of the city, as well as people who regularly socialise, shop or work within the city, and live in small towns and rural areas surrounding the city. It is important to note that GCCSAs do not define the built up edge of the city. They provide a stable definition for these cities and are designed for the output of a range of social and economic survey data.

This statement has been prepared based on information available at 11 am on Thursday 1 March 2018. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

In some situations, some or all of the rainfall is in the form of hail or snow. In these cases the totals given are for the water equivalent: the depth of liquid water that results from melting any frozen precipitation. There can be significant 'undercatch' of snow in strong winds, meaning the true precipitation can be higher than that reported.

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.

Where temperature area averages are mentioned, they are derived from the ACORN-SAT dataset.

Further information

Media
(03) 9669 4057
Enquiries