Greater Perth in autumn 2018: Dry despite late season rain

Rainfall in autumn 2018 was below average across the Greater Perth Area due to a dry March and April, despite some moderate to heavy rain in late May. Mean maximum and minimum temperatures were mostly above average.

Below average rainfall across Perth

  • Rainfall in autumn 2018 was about 50% to 70% of normal, with totals generally between 80 mm and 120 mm for coastal plain sites and offshore Islands, and 160 mm-200 mm in the hills
  • Rainfall during autumn was mostly infrequent with modest totals, however late in May a strong cold front and associated deep low produced four consecutive wet days with moderate to heavy falls between 24 and 28 May
  • Bickley recorded 67.0 mm in the 24 hours to 9am on 26 May, which was its wettest autumn day for thirteen autumn seasons, since a daily total of 72.0 mm was recorded on 19 May 2005

Above average temperatures for most Perth sites

  • Mean maximum temperatures were generally between 0.5 °C and 1.5 °C above average, and the warmest autumn since 2011 or 2012 for coastal plain sites
  • Mean minimum temperatures were generally between 0.2 °C and 0.6 °C warmer than normal

Perth Metro

  • Total rainfall for Perth Metro was 90.6 mm, which was the driest autumn for nine years when a seasonal total of 57.8 mm was recorded in autumn 2009
  • The mean maximum temperature for Perth Metro in autumn was 26.6 °C, which was the warmest autumn for six seasons, since autumn 2012 with a seasonal mean of 27.0 °C
  • The warmest day was 13 March when a maximum of 38.5 °C was recorded, and the coolest day was 28 May when the temperature reached only 17.2 °C
  • Perth Metro registered a late season record on 12 May when it recorded a maximum of 32.7 °C, the highest temperature on record so late in autumn.
  • The mean minimum temperature for Perth Metro was 13.9 °C, which was warmer than last autumn but cooler than autumn 2016
  • The coldest morning was on 20 May when a minimum of 5.1 °C was recorded, and the warmest morning occurred on 6 March when the minimum temperature was 25.5 °C

Further information

Media
(03) 9669 4057
Enquiries

Extremes in autumn 2018
Hottest day 38.6 °C at Millendon (Swan Valley) on 13 Mar
38.6 °C at Pearce RAAF on 13 Mar
Warmest days on average 27.9 °C at Pearce RAAF
Coolest days on average 24.0 °C at Bickley
Coldest day 14.5 °C at Bickley on 26 May
Coldest night 3.1 °C at Pearce RAAF on 4 May
Coolest nights on average 12.5 °C at Bickley
Warmest nights on average 17.4 °C at Rottnest Island
16.1 °C at Mandurah
Warmest night 26.0 °C at Millendon (Swan Valley) on 6 Mar
26.0 °C at Pearce RAAF on 6 Mar
Warmest on average overall 20.7 °C at Rottnest Island
20.6 °C at Swanbourne
Coolest on average overall 18.3 °C at Bickley
Wettest overall 205.8 mm at Bickley
Wettest day 67.0 mm at Bickley on 26 May
Strongest wind gust 104 km/h at Ocean Reef on 25 May


Summary statistics for autumn 2018
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean for
autumn
2018
Diff
from
average
Highest for
autumn
2018
Mean for
autumn
2018
Diff
from
average
Lowest for
autumn
2018
Total for
autumn
2018
Average
for
autumn
Rank of
autumn
2018
Fraction of
autumn
average
Bickley 24.0 +0.4 35.4 13 Mar 12.5 0.0 6.7 4 May 205.8 212.2 average 97%
Garden Island HSF 24.4 +0.4 37.0 13 Mar 16.5 +0.4 10.6 4 May 79.0 128.4 v low 62%
Jandakot Aero 26.5 +0.7 37.6 13 Mar 13.0 +0.6 4.9 20 May 115.6 164.9 low 70%
Mandurah 24.8 +0.5 34.7 13 Mar 16.1 +0.3 9.9 4 May 92.2 144.0 low 64%
Millendon (Swan Valley) 27.5   38.6 13 Mar 13.0   3.6 20 May 94.8
Pearce RAAF 27.9 +1.6 38.6 13 Mar 13.3 -0.1 3.1 4 May 79.6 135.1 low 59%
Perth Airport 27.1 +1.4 38.5 13 Mar 13.5 +0.4 4.9 4 May 83.2 154.6 low 54%
Perth Metro 26.6 +0.7 38.5 13 Mar 13.9 +0.2 5.1 20 May 90.6 144.9 low 63%
Rottnest Island 24.1 +0.5 35.3 21 Mar 17.4 +0.3 12.5 25 May 84.2 126.0 low 67%
Swanbourne 25.5 0.0 37.7 13 Mar 15.7 +0.6 8.8 30 May 107.8 152.1 average 71%

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.

In September 2017 this summary was broadened to include 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 Friday 1 June 2018. 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