Greater Perth in autumn 2020: average autumn rainfall

Rainfall in autumn 2020 was mostly close to season average in Greater Perth. Mean minimum temperatures were mostly slight above average across Perth. Mean maximum temperatures were above average for many sites but below average along the coastal suburbs and in the Perth hills.

Average rainfall in Greater Perth

  • Autumn rainfall was mostly near average, due to a wet March, and a wet end of May
  • Seasonal rainfall totals were in the 100–170 mm range, and up to 210–250 mm in the Perth hills
  • The wettest days of the season with widespread moderate rainfall across Perth were the 25th, 29th and 30th of May; Mundaring recorded the highest daily rainfall of 41.2mm on the 30th

Autumn nights slightly warmer than normal

  • Mean maximum temperatures were above average for many sites, but below average along the coastal suburbs and in the Perth hills
  • The hottest day of the season was the 11th of April, when daily maximum temperatures climbed over 40 °C at Pearce RAAF (40.7 °C) and Milendon (40.4 °C), and many April temperatures records were set
  • Mean minimum temperatures were slightly above average across Greater Perth
  • The coldest nights of the season were between 19 and 21 May and the lowest temperature was 1.7 °C at Jandakot Aero on the 19th and also at Pearce RAAF on the 21st.

Perth Metro

  • Total rainfall for Perth Metro was 157.6 mm, which is 111% of the long-term average of 142.6 mm
  • The mean daily maximum temperature for Perth Metro was 26.0 °C, which is 0.1 °C above the long-term average of 25.9 °C
  • The warmest day was 39.5 °C on 11 April, and the coolest day was on 6 May when the temperature reached 16.9 °C
  • The mean daily minimum temperature for Perth Metro was 13.9 °C, which is 0.2 °C above the long-term average of 13.7 °C
  • The coldest morning was 4.6 °C on 19 May, and the warmest morning was on 14 March when the minimum temperature was 22.8 °C

Further information

Media
(03) 9669 4057

Extremes in autumn 2020
Hottest day 40.7 °C at Pearce RAAF on 11 Apr
Warmest days on average 27.3 °C at Pearce RAAF
Coolest days on average 23.3 °C at Bickley
Coldest day 12.6 °C at Bickley on 6 May
12.6 °C at Bickley on 25 May
Coldest night 1.7 °C at Jandakot Aero on 19 May
1.7 °C at Pearce RAAF on 21 May
Coolest nights on average 12.8 °C at Bickley
Warmest nights on average 17.3 °C at Rottnest Island
Warmest night 23.7 °C at Pearce RAAF on 25 Mar
Warmest on average overall 20.6 °C at Rottnest Island
Coolest on average overall 18.1 °C at Bickley
Wettest overall 248.8 mm at Jarrahdale
Driest overall 98.2 mm at Muchea
Wettest day 41.2 mm at Mundaring on 30 May
Strongest wind gust 113 km/h at Rottnest Island on 5 May




Summary statistics for autumn 2020
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean for
autumn
2020
Diff
from
average
Highest for
autumn
2020
Mean for
autumn
2020
Diff
from
average
Lowest for
autumn
2020
Total for
autumn
2020
Average
for
autumn
Rank of
autumn
2020
Fraction of
autumn
average
Bickley 23.3 -0.3 36.5 11 Apr 12.8 +0.4 6.1 9 May 242.6 210.5 average 115%
Garden Island HSF 24.2 +0.2 37.1 11 Apr 16.4 +0.3 7.6 15 May
Gosnells City 26.4 -0.2 39.5 11 Apr     6.7 11 May        
Jandakot Aero 25.9 +0.1 39.2 11 Apr 13.2 +0.8 1.7 19 May 169.0 163.0 average 104%
Karnet 23.5 0.0 36.6 11 Apr 12.0 +0.3 3.3 19 May 209.5 230.1 average 91%
Mandurah 24.2 -0.1 35.2 9 Mar 16.1 +0.3 8.6 10 May 98.8 137.9 low 72%
Millendon (Swan Valley) 26.8   40.4 11 Apr 13.1   2.8 21 May 109.0
Pearce RAAF 27.3 +0.9 40.7 11 Apr 13.5 +0.1 1.7 21 May 99.8 133.2 low 75%
Perth Airport 26.4 +0.7 39.6 11 Apr 13.3 +0.2 2.3 19 May 149.6 153.2 average 98%
Perth Metro 26.0 +0.1 39.5 11 Apr 13.9 +0.2 4.6 19 May 157.6 142.6 average 111%
Rottnest Island 23.9 +0.3 35.2 11 Apr 17.3 +0.2 11.1 6 May 101.8 121.8 average 84%
Swanbourne 25.0 -0.4 37.3 11 Apr 15.7 +0.6 6.7 19 May 123.0 147.4 average 83%

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 10 am on Monday 1 June 2020. 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