Greater Perth in spring 2020: a wet end to spring with mild temperatures

Spring rainfall was above average across Greater Perth largely due to a record wet November, after a dry October. Mean maximum temperatures were mostly warmer than average and mean minimum temperatures were above average across Greater Perth this spring.

Dry October and record wet November

  • Spring rainfall was above average due to a record wet November; rainfall totals ranged from 110–190 mm, up to 310–350 mm in the Perth hills.
  • Perth Metro recorded 182.0 mm this spring, which was its sixth-wettest spring on record and the wettest since 2013.

Above average temperatures

  • Spring mean maximum temperatures were generally less than 1 °C above average for coastal plain sites away from the coast and Perth hills.
  • Spring mean minimum temperatures were 0.5–1.0 °C above average for most sites.
  • Perth Metro recorded two very hot days with temperatures over 35 °C this spring: one was 36.6 °C on 30 October which was its fourth-highest October temperature on record, and another was 35.1 °C on 23 November.
  • The highest temperature of the season in Greater Perth was 36.8 °C at Pearce RAAF on 30 October; the lowest temperature of the season was 3.7 °C at Perth Airport on 3 October.

Perth Metro

  • Total rainfall for Perth Metro was 182.4 mm, which is 124% of the long-term average of 147.4 mm
  • The mean daily maximum temperature for Perth Metro was 23.9 °C, which is 0.4 °C above the long-term average of 23.5 °C
  • The warmest day was 36.6 °C on 30 October, and the coolest day was on 2 October when the temperature reached 16.7 °C
  • The mean daily minimum temperature for Perth Metro was 12.4 °C, which is 0.6 °C above the long-term average of 11.8 °C
  • The coldest morning was 5.6 °C on 12 September, and the warmest morning was on 31 October when the minimum temperature was 17.6 °C

Possible tornado at Bertram suburb in September

  • A swathe of damage at the suburb of Bertram was consistent with a possible tornado during the passage of a cold front on 6 September. Damage was mostly minor with fences down, garage doors damaged and roof tiles off.

Further information

Media
(03) 9669 4057

Extremes in spring 2020
Hottest day 36.8 °C at Pearce RAAF on 30 Oct
Warmest days on average 24.5 °C at Millendon (Swan Valley)
24.5 °C at Pearce RAAF
Coolest days on average 21.1 °C at Bickley
21.1 °C at Rottnest Island
Coldest day 12.6 °C at Bickley on 2 Oct
Coldest night 3.7 °C at Perth Airport on 3 Oct
Coolest nights on average 10.2 °C at Bickley
Warmest nights on average 14.7 °C at Rottnest Island
Warmest night 20.6 °C at Garden Island HSF on 24 Nov
Warmest on average overall 18.2 °C at Mandurah
Coolest on average overall 15.6 °C at Bickley
Wettest overall 348.2 mm at Bickley
Driest overall 111.8 mm at Rottnest Island
Wettest day 63.4 mm at Mundaring on 10 Nov
Strongest wind gust 96 km/h at Swanbourne on 19 Sep

Record highest spring daily rainfall
New record
(mm)
Old
record
Years of
record
Araluen 59.2 on 7 Sep 56.0 on 29 Sep 2001 55



Highest spring total rainfall for at least 20 years
Observed
(mm)
Most recent
higher
Average for
spring
Gidgegannup 262.4 268.0 in 1983* 173.2

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




Summary statistics for spring 2020
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean for
spring
2020
Diff
from
average
Highest for
spring
2020
Mean for
spring
2020
Diff
from
average
Lowest for
spring
2020
Total for
spring
2020
Average
for
spring
Rank of
spring
2020
Fraction of
spring
average
Bickley 21.1 -0.2 33.5 24 Nov 10.2 +0.2 4.1 3 Oct 348.2 231.0 v high 151%
Garden Island HSF 21.3 0.0 33.2 30 Oct 14.3 +0.5 9.1 3 Oct
Jandakot Aero 23.5 +0.3 35.4 30 Oct 11.4 +1.2 4.2 12 Sep 179.8 159.6 average 113%
Karnet     33.2 23 Nov     3.9 13 Sep        
Mandurah 22.3 +0.3 33.4 30 Oct 14.1 +0.5 8.1 3 Oct 144.8 117.4 high 123%
Millendon (Swan Valley) 24.5   36.4 24 Nov 11.0   4.0 3 Oct 191.4
Pearce RAAF 24.5 +0.8 36.8 30 Oct 11.5 +1.0 4.7 3 Oct
Perth Airport 24.1 +1.1 36.1 23 Nov 11.4 +0.7 3.7 3 Oct 183.2 141.2 high 130%
Perth Metro 23.9 +0.4 36.6 30 Oct 12.4 +0.6 5.6 12 Sep 182.4 147.4 high 124%
Rottnest Island 21.1 +0.3 32.0 25 Oct 14.7 +0.4 7.7 3 Oct 111.8 100.0 average 112%
Swanbourne 22.3 -0.3 35.3 30 Oct 13.5 +0.8 6.8 3 Oct

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 Tuesday 1 December 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

Climate