Greater Perth in 2021: wet, a very warm start and finish

Annual rainfall was above average in 2021 across Greater Perth, due to a very wet July and October. Annual mean maximum and minimum temperatures were generally close to average.

Above average rainfall across Greater Perth

  • Rainfall was above average across Greater Perth, with annual rainfall totals mostly in the 800–900 mm range, to 1000–1300 mm in the Perth hills.
  • Swanbourne had its highest annual rainfall on record, and a number of sites had their highest for at least 20 years.
  • Perth Metro recorded a rainfall total of 892 mm in 2021, which was more than 150 mm above the annual average, and the second-highest annual rainfall on record, behind the record of 904.8 mm in 1995.
  • The wettest month of the year was July across Greater Perth; Perth Metro had its second-wettest July on record with 271.4 mm, just behind the record of 278. 6 mm in July 1995.
  • October was also very wet; Perth Metro had its wettest October on record with 122.8 mm at the current site, which was also the wettest October since 1965 in the Perth official records when 126.3 mm was recorded at Perth Regional Office.

Very warm January and an extreme heatwave in December

  • Annual mean maximum temperatures were generally within half a degree of average for most sites.
  • Annual mean minimum temperatures were close to or slightly above average at most sites.
  • The start of the year (January) was very warm, and an extreme heatwave occurred at the end of the year (December).
  • Perth Metro recorded 5 days in total with maximum temperatures of 40 °C or higher in December, which was the highest count of such days for any month in the Perth official records.
  • During the extreme heatwave in late December, Perth Metro recorded four consecutive days with maximum temperatures of 40 °C or higher between the 25th and the 28th, which was the equal longest run in the Perth official records.
  • The hottest days of the year were either the 25th or 26th of December; Rottnest Island recorded its all-time highest temperature on record with 42.5 °C and also all-time highest minimum temperature on record with 27.0 °C on the 26th.
  • Perth Metro recorded its third-highest temperature on the 25th ( 42.8 °C) and second-highest temperature on the 26th (43.5 °C) for December in the Perth official records commencing in 1897.

Perth Metro

  • Total rainfall for Perth Metro was 892.0 mm, which is 121% of the long-term average of 736.8 mm
  • The mean daily maximum temperature for Perth Metro was 25.0 °C, which is 0.2 °C above the long-term average of 24.8 °C
  • The warmest day was 43.5 °C on 26 December, and the coolest day was on 2 September when the temperature reached 13.9 °C
  • The mean daily minimum temperature for Perth Metro was 13.2 °C, which is 0.3 °C above the long-term average of 12.9 °C
  • The coldest morning was 1.1 °C on 26 June, and the warmest morning was on 9 December when the minimum temperature was 26.8 °C

Further information

Media
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Extremes in 2021
Hottest day 43.7 °C at Swanbourne on 26 Dec
Warmest days on average

25.7 °C at Pearce RAAF

Coolest days on average 22.3 °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

11.6 °C at Bickley

Warmest nights on average 15.8 °C at Rottnest Island
Warmest night 28.0 °C at Pearce RAAF on 26 Dec
Warmest on average overall 19.3 °C at Pearce RAAF
Coolest on average overall 17.0 °C at Bickley
Wettest overall 1384.3 mm at Huntly
Wettest day 77.0 mm at Huntly on 27 Jul
Strongest wind gust 115 km/h at Rottnest Island on 1 Aug

Record highest annual total rainfall
New record
(mm)
Old
record
Years of
record
Annual
average
Swanbourne 951.8 873.0 in 1996 25 737.1

Highest annual total rainfall for at least 20 years
Observed
(mm)
Most recent
higher
Annual
average
Pearce RAAF 787.0 970.0 in 1974* 654.7
Bickley 1312.0 1410.3 in 1996 1086.7
Karnet 1306.9 1509.8 in 1991* 1153.5
Marbling 891.8 909.1 in 1992* 756.9
Perth Metro 892.0 904.8 in 1995* 736.8
Karragullen North 1177.2 1189.8 in 1981* 1000.2
Serpentine 939.2 1050.5 in 1974* 918.6
Jarrahdale 1231.8 1312.2 in 1992* 1169.7

* note: there are gaps in the historical record at this site, so it is possible a higher value has gone unreported




Record highest temperature
New record
(°C)
Old
record
Years of
record
Annual
average
Rottnest Island 42.5 on 26 Dec 41.5 on 26 Feb 1997 36 22.3



Record highest daily minimum temperature
New record
(°C)
Old
record
Years of
record
Annual
average
Rottnest Island 27.0 on 27 Dec 26.4 on 28 Jan 2012 36 15.7



Summary statistics for 2021
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean
for
2021
Diff
from
average
Highest
for
2021
Mean
for
2021
Diff
from
average
Lowest
for
2021
Total
for
2021
Average
annual
total
Rank
of
2021
Fraction
of annual
average
Bickley 22.3 -0.3 40.3 26 Dec 11.6 +0.3 3.6 22 Jun 1312.0 1086.7 high 121%
Garden Island HSF 22.9 +0.2 42.5 26 Dec 14.9 -0.1 6.0 2 Aug 833.2 610.4 v high 137%
Jandakot Aero 24.8 +0.2 43.3 26 Dec 12.4 +0.8 0.1 22 Jun 922.6 818.4 high 113%
Mandurah     41.0 26 Dec 14.9 +0.1 6.5 2 Aug 678.4 649.2 average 104%
Millendon (Swan Valley) 25.5   42.9 26 Dec 12.4   0.4 26 Jun 752.2
Pearce RAAF 25.7 +0.4 43.3 25 Dec 12.8 +0.6 1.4 22 Jun 787.0 654.7 high 120%
Perth Airport 25.3 +0.7 43.3 26 Dec 12.7 +0.5 0.5 22 Jun 798.8 760.9 average 105%
Perth Metro 25.0 +0.2 43.5 26 Dec 13.2 +0.3 1.1 26 Jun 892.0 736.8 v high 121%
Rottnest Island 22.7 +0.4 42.5 26 Dec 15.8 +0.1 7.2 2 Aug 660.6 567.7 high 116%
Swanbourne 23.7 -0.4 43.7 26 Dec 14.3 +0.3 5.1 22 Jun 951.8 737.1 highest 129%

Notes

The Annual climate summary, generally published on the second working day of the year, 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 5 pm on Monday 7 February 2022. 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