Greater Perth in winter 2021: very wet July sandwiched between a dry June and August

Rainfall was generally close to average to above average across Greater Perth, due to very wet July alleviating a dry June and August. Mean minimum temperatures were above average although mean maximum temperatures were mixed.

Very wet July alleviating a dry June and August

  • Winter rainfall was close to average to above average at most sites in Greater Perth, with seasonal rainfall totals generally in the 400–500 mm range, to 600–730 mm in the Perth hills.
  • Perth Metro recorded 421.6 mm in total, which was 7% above winter average rainfall; winter rainfall in 2021 was more than 100 mm higher than in winter 2020 (291.8 mm), but was 12 mm less than in winter 2019 (434.8 mm) at Perth Metro.
  • Perth Metro recorded 57 days in total with daily rainfall of at least 0.2 mm, which was the third-highest number of rain days in winter on record at Perth Metro site, behind 63 rain days in 1996 and 58 rain days in 2000.
  • July was very wet across Greater Perth; Perth Metro had its second-wettest July on record with a total of 271.4 mm, behind 278.6 mm in 1995, and it was the tenth-wettest July on record in the official Perth city records commencing in 1876.
  • Several sites in the Perth hills recorded July rainfall totals in excess of 400 mm, and the last time that Greater Perth saw July rainfall totals of at least 400 mm was 57 years ago in 1964; Bickley's 459.2 mm in July was its annual highest monthly rainfall on record with observations commencing in 1969.
  • The wettest winter days were on the 5th, 10th, 21st and 27th of July with daily rainfall totals mostly in the 30–60 mm range; daily rainfall of 60–80 mm were recorded along the Perth hills and in the southern suburbs on the 27th, and Anketell had its highest winter daily rainfall in 20 years of record.

Above average overnight temperatures

  • Mean minimum temperatures were above average across Greater Perth, although mean maximum temperatures were mixed.
  • Perth Metro recorded a mean maximum temperature of 18.9 °C, which was just 0.1 °C below average and the coolest winter since 2018.
  • Perth Metro recorded a mean minimum temperature of 9.0 °C, which was 0.7 °C above average, although winter 2020 was warmer (9.5 °C).
  • June was cold, and it was the lowest-June mean temperature for 26 years since 1995 at several sites including Perth Metro (12.9 °C).
  • The warmest winter days were on the 16th and 17th with daily maxima mostly in the mid-20s, and the coldest winter day was on the 10th with daily maxima were in the mid-10s, all in the month of August.
  • The coldest nights were on the 22th and 26th of June with daily minima below 2 °C at the coastal plain sites.

Perth Metro

  • The warmest day was 25.1 °C on 17 August, and the coolest day was on 21 June when the temperature reached 14.4 °C.
  • The coldest morning was 1.1 °C on 26 June, and the warmest morning was on 13 July when the minimum temperature was 13.9 °C.

Fifteen days of damaging wind gusts recorded in Greater Perth during winter

  • During winter, there were 15 days of damaging wind gusts in excess of 90 km/h recorded along the coast or at inland sites in Greater Perth, comprising 3 in June, 9 in July and 3 in August.
  • The Rottnest Island site recorded 13 such damaging wind gusts, the highest number in winter since 2003.

Further information

Media
(03) 9669 4057

Extremes in winter 2021
Hottest day 26.1 °C at Perth Airport on 17 Aug
Warmest days on average 18.9 °C at Perth Airport
18.9 °C at Perth Metro
Coolest days on average 15.4 °C at Bickley
Coldest day 10.3 °C at Bickley on 1 Aug
10.3 °C at Bickley on 10 Aug
Coldest night 0.1 °C at Jandakot Aero on 22 Jun
Coolest nights on average 7.2 °C at Karnet
Warmest nights on average 12.9 °C at Rottnest Island
Warmest night 17.3 °C at Garden Island HSF on 26 Jul
Warmest on average overall 15.6 °C at Rottnest Island
Coolest on average overall 11.7 °C at Bickley
Wettest overall 726.4 mm at Jarrahdale
Wettest day 77.0 mm at Huntly on 27 Jul
Strongest wind gust 115 km/h at Rottnest Island on 1 Aug

Record highest winter daily rainfall
New record
(mm)
Old
record
Years of
record
Anketell 67.2 on 27 Jul 61.2 on 9 Aug 2017 20


Summary statistics for winter 2021
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean for
winter
2021
Diff
from
average
Highest for
winter
2021
Mean for
winter
2021
Diff
from
average
Lowest for
winter
2021
Total for
winter
2021
Average
for
winter
Rank of
winter
2021
Fraction of
winter
average
Bickley 15.4 -0.4 22.8 17 Aug 8.2 +0.5 3.6 22 Jun 696.0 591.4 high 118%
Garden Island HSF 18.3 -0.1 24.4 16 Aug 11.8 +0.2 6.0 2 Aug 432.2 327.9 v high 132%
Jandakot Aero 18.6 0.0 25.3 16 Aug 8.2 +0.9 0.1 22 Jun 490.0 452.8 average 108%
Karnet 15.9 -0.1 22.9 17 Aug 7.2 +0.6 1.1 23 Jun        
Mandurah 17.8 -0.3 25.0 16 Aug 11.5 +0.4 6.5 2 Aug        
Millendon (Swan Valley) 18.8   25.6 17 Aug 8.2   0.4 26 Jun 400.8
Pearce RAAF 18.6 +0.2 25.5 17 Aug 9.0 +0.3 1.4 22 Jun 419.0 369.3 high 113%
Perth Airport 18.9 +0.4 26.1 17 Aug 8.8 +0.4 0.5 22 Jun 405.2 427.8 average 95%
Perth Metro 18.9 -0.1 25.1 17 Aug 9.0 +0.7 1.1 26 Jun 421.6 395.0 average 107%
Rottnest Island 18.4 +0.2 23.7 16 Aug 12.9 +0.2 7.2 2 Aug 316.8 303.4 average 104%
Swanbourne 18.5 -0.5 25.3 16 Aug 10.7 +0.5 5.1 22 Jun 462.2 393.5 high 117%

Notes

The Seasonal climate summary, generally published on the first working day of each month, lists the main features of the weather in Greater Perth 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.

This summary includes data from observing sites in or near the Greater Perth “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 9 am on Wednesday 1 September 2021. 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

Climate