Greater Perth in spring 2018: a dry start and finish to spring

Rainfall in spring 2018 was below average across Perth, with an average October sandwiched by a very dry September and November. Mean maximum temperatures were generally below average, while mean minimum temperatures were below average along the coast and on the Perth hills.

Below average rainfall

  • Spring rainfall was below average across Perth, with the season comprising a very dry September, an average October followed by a very dry November
  • Rottenest Island recorded 40 mm this spring, which was the driest spring in its 25 years of record
  • Perth Metro had a record dry September and November, resulting in a spring rainfall total of 78.4 mm, which was its driest spring since 2010 when 75.8 mm was recorded

Daytime temperatures mostly below average

  • Mean maximum temperatures were mostly below average
  • Mean minimum temperatures were below average along the coast and on the Perth hills

Perth Metro

  • Total rainfall for Perth Metro was 78.4 mm, which is 54% of the long-term average of 146.0 mm
  • The mean daily maximum temperature for Perth Metro was 23.1 °C, which is 0.4 °C below the long-term average of 23.5 °C
  • The warmest day was 35.9 °C on 16 Nov, and the coolest day was on 5 Sep when the temperature reached 15.7 °C
  • The mean daily minimum temperature for Perth Metro was 11.8 °C, equal to the long-term average
  • The coldest morning was 2.8 °C on 16 Sep, and the warmest morning was on 17 Nov when the minimum temperature was 18.3 °C

Further information

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Extremes in spring 2018
Hottest day 37.1 °C at Pearce RAAF on 16 Nov
Warmest days on average 24.1 °C at Pearce RAAF
Coolest days on average 20.2 °C at Garden Island HSF
20.2 °C at Rottnest Island
20.7 °C at Bickley
Coldest day 12.2 °C at Bickley on 5 Sep
Coldest night 1.4 °C at Bickley on 15 Sep
Coolest nights on average 9.6 °C at Bickley
Warmest nights on average 13.9 °C at Rottnest Island
13.0 °C at Mandurah
Warmest night 20.6 °C at Mandurah on 17 Nov
Warmest on average overall 17.4 °C at Pearce RAAF
17.4 °C at Perth Metro
Coolest on average overall 15.1 °C at Bickley
Wettest overall 168.5 mm at Karnet
Driest overall 40.0 mm at Rottnest Island
Wettest day 44.6 mm at Huntly on 14 Oct
Strongest wind gust 83 km/h at Garden Island HSF on 13 Oct

Record lowest spring total rainfall
New record
(mm)
Old
record
Years of
record
Average for
spring
Rottnest Island 40.0 41.8 in 2000 25 101.6



Summary statistics for spring 2018
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean for
spring
2018
Diff
from
average
Highest for
spring
2018
Mean for
spring
2018
Diff
from
average
Lowest for
spring
2018
Total for
spring
2018
Average
for
spring
Rank of
spring
2018
Fraction of
spring
average
Bickley 20.7 -0.5 32.4 16 Nov 9.6 -0.4 1.4 15 Sep 139.2 230.2 v low 60%
Garden Island HSF 20.2 -1.1 29.4 9 Oct 13.4 -0.4 6.9 15 Sep 48.0 113.2 v low 42%
Jandakot Aero 22.7 -0.4 35.0 16 Nov 10.6 +0.4 1.9 16 Sep 88.2 160.9 v low 55%
Mandurah 21.3 -0.7 33.6 16 Nov 13.0 -0.6 5.9 15 Sep 67.0 119.1 low 56%
Millendon (Swan Valley) 24.0   36.2 16 Nov 10.5   1.6 16 Sep 80.6
Pearce RAAF 24.1 +0.5 37.1 16 Nov 10.7 +0.2 2.5 16 Sep 67.8 126.7 v low 54%
Perth Airport 23.4 +0.4 36.0 16 Nov 11.1 +0.5 2.6 16 Sep 77.8 141.5 v low 55%
Perth Metro 23.1 -0.4 35.9 16 Nov 11.8 0.0 2.8 16 Sep 78.4 146.0 v low 54%
Rottnest Island 20.2 -0.6 27.8 9 Oct 13.9 -0.4 8.3 15 Sep 40.0 101.6 lowest 39%
Swanbourne 21.3 -1.3 31.9 9 Nov 12.6 -0.1 6.0 15 Sep 75.0 147.2 v low 51%

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 9 am on Monday 3 December 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