Greater Perth in autumn 2019: very dry, below average night-time temperatures

It was a very dry autumn across Greater Perth, with seasonal rainfall totals well below average. Mean minimum temperatures were all below average. Mean maximum temperatures were near average to above average in inland suburbs and the Perth hills, in contrast to below average mean maximum temperatures along the coast and at offshore islands.

A very dry autumn across Greater Perth

  • It was a very dry autumn across Greater Perth, with seasonal rainfall less than half of the seasonal average; rainfall totals ranged in the 40-80 mm for most sites, with up to 100-110 mm in the Perth hills
  • Perth Metro recorded a seasonal rainfall total of 68.2 mm (6.2 mm in March, 44.2 mm in April, 17.8 mm in May), which was its driest autumn for 10 years when 57.8 mm was recorded in autumn 2009
  • It was the driest autumn on record at Pearce RAAF, and driest autumn since 1983 at Perth Airport, Rottnest Island, Mundaring and Maida Vale

Below average night-time temperatures

  • Mean maximum temperatures were near average to above average in inland suburbs and the Perth hills, in contrast to below average mean maximum temperatures along the coast and at offshore islands
  • Mean minimum temperatures were mostly within 1 °C below average
  • Perth Metro recorded a mean minimum temperature of 12.9 °C, which was 0.8 °C below average, and the coolest autumn for 10 years when a mean minimum of 12.7 °C was recorded in autumn 2009
  • Swanbourne had its lowest autumn temperature on record on 18 May
  • Pearce RAAF claimed both highest and lowest temperatures of the season in Greater Perth with 41.1 °C on 4 March and -0.3 °C on 18 May

Perth Metro

  • Total rainfall for Perth Metro was 68.2 mm, which is 48% of the long-term average of 142.0 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 4 Mar, and the coolest day was on 17 May when the temperature reached 16.7 °C
  • The mean daily minimum temperature for Perth Metro was 13.0 °C, which is 0.7 °C below the long-term average of 13.7 °C. The coldest morning was 1.6 °C on 19 May, and the warmest morning was on 21 Mar when the minimum temperature was 21.8 °C

Further information

Media
(03) 9669 4057
Enquiries

Extremes in autumn 2019
Hottest day 41.1 °C at Pearce RAAF on 4 March
Warmest days on average 27.5 °C at Pearce RAAF
Coolest days on average 23.3 °C at Rottnest Island
Coldest day 13.1 °C at Bickley on 19 April
Coldest night -0.3 °C at Pearce RAAF on 18 May
Coolest nights on average 11.8 °C at Bickley
Warmest nights on average 16.5 °C at Rottnest Island
Warmest night 23.3 °C at Mandurah on 19 March
Warmest on average overall 19.9 °C at Pearce RAAF and at Rottnest Island
Coolest on average overall 17.7 °C at Bickley
Wettest overall 132.0 mm at Huntly
Driest overall 37.8 mm at Rottnest Island
Wettest day 32.0 mm at Huntly on 19 April
Strongest wind gust 91 km/h at Garden Island HSF and Rottnest Island, both on 19 April

Record lowest autumn total rainfall

New record
(mm)
Old
record
Years of
record
Average for
autumn
Pearce RAAF 48.2 50.2 in 1983 63 133.7
Gidgegannup 62.4 71.4 in 2009 57 173.4
Rottnest Island 37.8 42.0 in 2009 26 122.6

Lowest autumn total rainfall for at least 20 years

Observed
(mm)
Most recent
lower
Average for
autumn
Perth Airport 51.0 43.0 in 1983 153.3
Mundaring 91.7 54.6 in 1983* 209.9
Maida Vale 60.8 46.2 in 1983* 155.0

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




Record lowest autumn temperature

New record
(°C)
Old
record
Years of
record
Average for
autumn
Swanbourne 4.8 on 18 May 5.0 on 31 May 2013 26 15.1



Summary statistics for autumn 2019

Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean for
autumn
2019
Diff
from
average
Highest for
autumn
2019
Mean for
autumn
2019
Diff
from
average
Lowest for
autumn
2019
Total for
autumn
2019
Average
for
autumn
Rank of
autumn
2019
Fraction of
autumn
average
Bickley 23.6 0.0 37.2 4 Mar 11.8 -0.7 3.5 19 May 98.4 209.9 v low 47%
Garden Island HSF 23.7 -0.4 36.5 4 Mar 15.2 -0.9 7.8 18 May 59.0 124.6 v low 47%
Jandakot Aero 25.9 +0.1 39.7 4 Mar 12.1 -0.3 -0.1 19 May 74.8 162.9 v low 46%
Mandurah 24.1 -0.3 37.2 4 Mar 14.9 -0.9 6.5 18 May 78.6 140.2 low 56%
Millendon (Swan Valley) 26.9   40.7 4 Mar 12.4   0.5 18 May 49.4


Pearce RAAF 27.5 +1.2 41.1 4 Mar 12.3 -1.1 -0.3 18 May 48.2 133.7 lowest 36%
Perth Airport 26.5 +0.8 40.4 4 Mar 12.6 -0.5 1.5 18 May 51.0 153.3 v low 33%
Perth Metro 26.0 +0.1 39.5 4 Mar 13.0 -0.7 1.6 19 May 68.2 142.0 v low 48%
Rottnest Island 23.3 -0.3 33.8 31 Mar 16.5 -0.6 9.8 18 May 37.8 122.6 lowest 31%
Swanbourne 24.8 -0.7 39.4 4 Mar 14.6 -0.5 4.8 18 May 58.4 148.3 v low 39%

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 2 pm on Saturday 1 June 2019. 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