Greater Perth in May 2018: Warm days before rain in late May

May rainfall was slightly below average for most Perth sites with most of the rain falling towards the end of month. Mean maximum temperatures were very much above average, while the mean minimum temperatures were generally below average for the Perth coastal plain sites.

Near average to below average rainfall

  • Monthly rainfall totals were between 50 mm and 80 mm for coastal plain sites, and 120 mm -150 mm in the hills
  • A strong cold front and associated deep low produced four consecutive wet days with moderate to heavy falls between the 24th and 28th; the wettest day of the month being the 25th or 26th
  • Bickley recorded a daily rainfall of 67.0 mm on the 26th, which was its wettest May day for thirteen years, since a daily total of 72.0 mm was recorded on 19 May 2005

Above average mean maximum temperatures; Below average mean minimum temperatures for costal plain sites

  • Mean maximum temperatures were mostly 1 °C to 3 °C above average across the Perth area
  • Rottnest Island had its warmest May on record; Pearce RAAF had its warmest May for 46 years
  • Days were persistently warm in the middle of the month, as Perth Metro, Perth Airport and Pearce RAAF all recorded 16 consecutive days with maxima 24 °C or higher between the 9th and 24th.The previous record for such a spell at Perth Airport was 12 days between 18 and 29 May 1972, whilst the Perth city had 11 consecutive days of 24 °C between 1 and 11 May 1962
  • Mean minimum temperatures were mostly below average for the coastal plain sites and in the hills
  • Pearce RAAF recorded a minimum temperature of 19.3 °C on the 12th, which was its warmest morning in May for fifteen years when a minimum of 20.3 °C was recorded on 1 May 2003

Perth Metro

  • Total rainfall for Perth Metro was 67.4 mm, and was Perth Metro's driest May since 2012, when a total of 49.0 mm was recorded
  • The mean maximum temperature for Perth Metro was 23.9 °C, which was its warmest May for nine years when a mean of 24.4 °C was recorded on May 2009 (Perth Metro's warmest May on record)
  • A daily maximum temperature of 32.7 °C on the 12th was the highest temperature in May for 15 years when a maximum of 32.7 °C was recorded on 1 May 2003. It was also the highest temperature recorded so late in May for the Perth city. The previous latest date in May with temperature of 32 °C in the city was 3 May in 1907 (32.2 °C)
  • The mean minimum temperature for Perth Metro was 10.0 °C, which was cooler than last two years but warmer than 2014
  • The coldest morning was 5.1 °C on the 20th, and the warmest morning was on the 12th when the minimum temperature was 15.2 °C

Further information

Media
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Extremes in May 2018
Hottest day 34.1 °C at Pearce RAAF on the 12th
Warmest days on average 24.6 °C at Pearce RAAF
Coolest days on average 20.5 °C at Bickley
Coldest day 14.5 °C at Bickley on the 26th
Coldest night 3.1 °C at Pearce RAAF on the 4th
Coolest nights on average 9.4 °C at Jandakot Aero
Warmest nights on average 15.7 °C at Rottnest Island
13.6 °C at Mandurah
Warmest night 19.3 °C at Pearce RAAF on the 12th
Warmest on average overall 19.1 °C at Rottnest Island
18.3 °C at Swanbourne
Coolest on average overall 15.2 °C at Bickley
Wettest overall 151.6 mm at Bickley
Wettest day 67.0 mm at Bickley on the 26th
Strongest wind gust 104 km/h at Ocean Reef on the 25th

Record highest May mean daily maximum temperature
New record
(°C)
Old
record
Years of
record
Average for
May
Rottnest Island 22.6 22.5 in 2009 28 21.1

Highest May mean daily maximum temperature for at least 20 years
Observed
(°C)
Most recent
higher
Average for
May
Pearce RAAF 24.6 24.9 in 1972 22.0



Summary statistics for May 2018
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean for
May
2018
Diff
from
average
Highest for
May
2018
Mean for
May
2018
Diff
from
average
Lowest for
May
2018
Total for
May
2018
Average
for
May
Rank of
May
2018
Fraction of
May
average
Bickley 20.5 +1.2 29.6 12th 9.8 -0.4 6.7 4th 151.6 131.9 high 115%
Garden Island HSF 23.0 +1.7 29.3 12th 14.1 +0.1 10.6 4th 44.4 75.4 low 59%
Jandakot Aero 23.7 +1.7 31.5 12th 9.4 0.0 4.9 20th 81.0 106.6 average 76%
Mandurah 22.3 +1.2 28.0 11th 13.6 +0.1 9.9 4th 66.0 90.6 average 73%
Millendon (Swan Valley) 24.3   34.0 12th 9.5   3.6 20th 71.0
Pearce RAAF 24.6 +2.6 34.1 12th 10.2 -0.5 3.1 4th 62.2 83.9 average 74%
Perth Airport 24.2 +2.4 33.1 12th 10.3 -0.1 4.9 4th 72.2 98.5 average 73%
Perth Metro 23.9 +1.6 32.7 12th 10.0 -0.5 5.1 20th 67.4 89.4 low 75%
Rottnest Island 22.6 +1.5 27.3 23rd 15.7 +0.5 12.5 25th 54.2 74.0 average 73%
Swanbourne 23.6 +1.4 30.4 12th 13.0 +0.4 8.8 30th 70.4 90.7 low 78%

Daily maximum temperatures for May 2018
12345678910111213141516171819202122232425262728293031
Bickley17.816.117.618.825.117.618.719.120.320.525.529.624.122.623.522.921.921.121.521.622.124.124.623.814.914.517.315.318.218.716.6
Garden Island HSF18.818.818.921.027.821.820.019.824.524.827.929.321.826.326.624.325.224.423.523.624.425.427.626.519.019.520.818.120.322.020.5
Gosnells City20.822.522.829.521.221.724.724.530.233.526.026.526.024.024.525.515.918.020.718.421.122.518.0
Jandakot Aero20.819.420.721.928.721.320.522.324.424.328.731.525.526.327.125.824.824.423.423.825.127.527.927.318.819.121.418.222.717.6
Karnet18.018.518.019.525.617.918.519.626.024.024.323.022.523.525.119.6
Mandurah19.719.219.820.623.821.120.420.924.525.328.024.723.725.725.723.424.724.622.923.123.023.323.824.318.519.020.418.319.421.119.9
Millendon (Swan Valley)21.419.620.922.329.322.422.722.525.325.129.734.026.426.827.326.425.124.624.624.926.028.028.528.018.218.721.418.221.622.120.4
Pearce RAAF21.520.321.322.530.022.622.722.925.625.129.934.126.627.027.626.425.124.524.324.926.028.129.128.319.619.420.819.322.023.222.6
Perth Airport21.320.321.322.129.422.122.222.724.824.729.533.126.326.227.326.325.124.424.324.925.728.028.427.720.618.821.018.321.522.919.5
Perth Metro21.119.220.922.128.821.721.522.524.624.428.932.725.326.127.026.324.924.324.324.625.428.128.627.418.819.321.317.221.222.319.1
Rottnest Island19.819.919.620.826.621.919.720.022.323.227.327.322.025.026.024.624.023.522.022.826.227.325.418.519.020.918.920.322.220.9
Swanbourne20.219.320.021.628.922.120.620.824.224.329.230.423.326.227.526.125.324.224.124.125.827.328.126.819.619.621.618.020.422.819.0
Values are the maximum temperature, usually in the 24 hours from 9 am on the day indicated,
and typically occurred in the afternoon of that day.
Temperatures coloured according to their difference
from the long-term average for the period
-10.0 -9.0 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 +1.0 +2.0 +3.0 +4.0 +5.0 +6.0 +7.0 +8.0 +9.0 +10.0 °C Grey outline marks highest
and lowest for the period

Daily minimum temperatures for May 2018
12345678910111213141516171819202122232425262728293031
Bickley10.09.07.66.77.812.68.89.19.710.711.513.515.412.610.010.89.28.48.38.79.38.89.711.810.610.311.67.88.16.99.8
Garden Island HSF15.515.413.310.612.318.213.213.413.215.417.016.514.516.015.314.513.213.913.611.212.715.714.312.914.514.115.213.112.311.115.4
Gosnells City12.011.88.08.916.19.210.011.917.019.013.715.015.29.213.410.013.013.013.08.58.08.512.0
Jandakot Aero9.79.36.75.56.615.16.16.58.914.815.415.011.111.915.110.07.38.46.14.95.66.86.87.712.613.414.67.65.88.0
Karnet8.98.08.510.011.07.68.015.010.59.05.010.08.58.210.510.57.78.1
Mandurah14.913.212.39.911.217.811.711.612.114.416.418.216.116.013.614.613.512.411.210.612.512.615.616.014.114.715.810.711.511.114.1
Millendon (Swan Valley)9.97.55.83.89.411.76.35.39.014.416.818.911.711.314.814.77.110.54.33.65.48.88.69.213.312.911.98.36.36.48.1
Pearce RAAF10.46.56.13.110.412.57.65.06.615.417.219.311.810.415.716.27.211.19.14.57.28.311.010.013.513.013.09.46.08.69.0
Perth Airport9.38.75.64.97.212.65.55.08.914.415.717.411.612.513.913.310.411.58.69.48.012.012.011.212.312.27.77.89.49.0
Perth Metro12.310.98.26.06.713.87.97.510.014.613.915.213.113.412.810.48.210.15.75.16.37.97.58.613.912.714.89.17.65.110.2
Rottnest Island16.114.014.612.814.418.415.214.714.915.717.118.818.517.216.216.816.415.815.315.116.216.618.412.512.916.015.613.414.316.2
Swanbourne15.413.311.39.010.117.211.410.912.314.916.018.816.615.414.314.111.912.09.310.111.113.413.514.714.112.915.811.99.68.813.2
Values are the minimum temperature, usually in the 24 hours to 9 am on the day indicated,
and typically occurred that morning.
Temperatures coloured according to their difference
from the long-term average for the period
-10.0 -9.0 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 +1.0 +2.0 +3.0 +4.0 +5.0 +6.0 +7.0 +8.0 +9.0 +10.0 °C Grey outline marks highest
and lowest for the period

Daily rainfall for May 2018
12345678910111213141516171819202122232425262728293031
Anketell - 0.8 0.6 - - 1.8 0.2 - - - - - - - - - - - - - - - - - 42.0 18.0 9.6 2.8 3.2 - -
Bickley - - 5.0 - - 5.2 1.2 - - 0.2 - - - - - - - - - - - - - - 41.8 67.0 27.6 3.2 0.2 0.2 -
Bungendore - - 0.4 - 0.2 1.6 2.2 0.2 0.2 - - - - - - - - - - - - - - - 39.8 27.0 16.0 8.4 0.2 0.2 -
Chidlow - - 1.6 - - 1.8 - - - - - - - - - - - - - - - - - - 26.0




Garden Island HSF 0.2 0.6 1.2 - - 1.0 - - - - - - - - - - - - - - - - - - 29.2 7.6 2.8 0.8 1.0 - -
Gidgegannup - - 2.8 - - 1.2 0.2 - - - - - - - - - - - - - - - - - 25.4 40.0 9.2 3.6 0.4 - -
Gosnells City - 0.4 - - - 3.2 - - - - - - - - - - - - - - - - 58.6 0.2 3.0 0.1 - -
Huntly 0.1 1.8 2.8 - - 1.8 2.6 - - - - - - 0.2 - - - - - - - - - - 53.2 40.8 9.4 8.4 0.2 -
Jandakot Aero - 0.4 1.4 - - 6.0 0.2 - - - - - - - - - - - - - - - - - 39.4 16.4 16.0 1.2 -
-
Jarrahdale - - 1.6 0.2 - 4.4 3.0 0.2 0.2 - - - - 0.2 - 0.2 0.2 - - 0.2 0.2 0.2 - - 38.8 39.4 12.0 6.6 0.6 0.2 -
Karnet - - 3.9 - - 4.2 4.3 0.1 -

- - - - - - - - - - - - 39.2 4.0 15.4 1.4
Karragullen North - - 0.6 - - 2.8 0.8 - - - - - - - - - - - - - - - - - 42.2 48.2 16.0 2.6


Maida Vale - - 3.0 - - 3.8 - - - - - - - - - - - - - - - - - - 33.2 38.4 8.6 2.0 0.2

Mandurah - 2.6 0.2 - - 0.8 0.2 - - - - - - - - - - - - - - - - - 38.8 9.4 5.0 8.4 0.6 - -
Midland - 5.1 1.3 - - - - - - - - - - - - - - - - - - - - - 37.5 - - - - 22.6
Millendon (Swan Valley) - - 2.8 - - 0.6 0.4 - - - - - - - - - - - - - - - - - 28.4 33.4 2.8 2.2 0.4 - -
Mount Solus - - 1.8 - - 2.6 0.8 0.2 - 0.2 - - - - - - - - - - - - - - 34.2 31.4 7.2 3.6 - 0.2 -
Muchea - - 1.2 - - 0.8 0.2 0.2 - - - - - - - - - - - - - - - - 31.4 20.4 3.2 6.0 0.2 - -
Mundaring - - 2.0 - - 2.4 1.0 - - - - - - - - - - - - - - - - - 32.8 30.8 23.2 6.2 0.4 - -
Noble Falls




1.4

















28.0 30.0 7.4 4.8 1.0

Pearce RAAF - - 1.2 - - 1.0 0.8 - - - - - - - - - - - - - - - - - 27.6 24.2 4.0 3.0 0.4 - -
Perth Airport - - 1.2 - - 2.0 0.2 - - - - - - - - - - - - - - - - - 31.6 27.6 5.6 3.8 0.2 - -
Perth Metro - - 2.6 - - 3.2 0.4 - - - - - - - - - - - - - - - - - 29.2 24.6 4.2 2.8 0.4 - -
Pinjarra Refinery - - - - - - - 0.4 - - 0.1 0.9 0.6 - - - - 2.0 - 0.2 - 23.8 0.5 - - - - - - - 1.4
Pinjarra South - 1.0 2.2 - - 3.4 0.6 - - - - - - - - - - - - - - - - - 34.6 15.0 5.0 3.4 0.8 - -
Roleystone - - - - - 3.6 - - - - - - - - - - - - - - - - - - 48.6 32.6 12.8 2.8


Rottnest Island - 0.4 - - - 0.6 - - - - - - 0.4 - - - - - - -

- - 43.0 7.6 1.6 - 0.6 - -
Serpentine - - 1.0 - - 4.8 1.0 - - - - - - - - - - - - - - - - - 34.2 17.4 5.8 2.2 - - 0.2
Swanbourne - - 1.0 - - 1.4 0.2 - - - - - - - - - - - - - - - - - 41.4 21.6 2.8 1.4 0.6 - -
Wanneroo - - - - 1.8 - - - - - - - - - - - - - - - - - 27.2 23.0

Werribee - - 1.4 - - 0.6 0.2 - - - - - - - - - - - - - - - - - 27.6 26.6 8.0 2.2 0.2 0.2 -
Whiteman Park - - 2.8 - - 2.0 0.4























Most values are the precipitation in the 24 hours to 9 am on the day indicated. Days marked with → are part of a longer accumulation, which is shown on the final day.
Values over 100 mm have been rounded to the nearest whole millimetre.
Days marked with - have a rainfall report of zero; days left blank have no rainfall report (which often indicates no rain fell).
Rainfalls coloured
according to the amount
0 1.0 5.0 10.0 15.0 25.0 50.0 100 150 200 300 400 600 millimetres

Notes

The Monthly 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 9 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