Greater Perth in September 2018: a very dry month

Rainfall was well below average across Perth, and it was the equal driest September at Perth Metro since recorded commenced in 1993. Daytime temperatures were slightly above average away from the coast while overnight temperatures were below average.

Below average rainfall

Below average minimum temperatures

  • Mean maximum temperatures were slight above average for the coastal plain sites and the Perth hills , but below average near along the coast and in the offshore islands
  • Mean minimum temperatures were half a degree to one degree below average across Perth
  • Perth Metro experienced four consecutive warm days with temperature of 25 °C between 20th and 23rd, which is its longest such run for six years since 14 to 17 September 2012
  • Cold mornings were experienced at the start and mid-September, and the lowest temperature of the month was 1.4 °C recorded at Bickley on the 15th

Perth Metro

  • Total rainfall for Perth Metro was 35.2 mm, which is 42% of the long-term average of 84.8 mm
  • The mean daily maximum temperature for Perth Metro was 20.5 °C, which is 0.2 °C above the long-term average of 20.3 °C. The warmest day was 28.0 °C on the 22nd, and the coolest day was on the 5th when the temperature reached 15.7 °C
  • The mean daily minimum temperature for Perth Metro was 8.8 °C, which is 0.8 °C below the long-term average of 9.6 °C. The coldest morning was 2.8 °C on the 16th, and the warmest morning was on the 14th when the minimum temperature was 12.9 °C

Further information

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Extremes in September 2018
Hottest day 28.7 °C at Millendon (Swan Valley) on the 22nd
Warmest days on average 20.9 °C at Millendon (Swan Valley)
Coolest days on average 17.7 °C at Bickley
Coldest day 12.2 °C at Bickley on the 5th
Coldest night 1.4 °C at Bickley on the 15th
Coolest nights on average 7.3 °C at Jandakot Aero
Warmest nights on average 12.4 °C at Rottnest Island
Warmest night 15.3 °C at Garden Island HSF on the 10th
15.3 °C at Rottnest Island on the 24th
Warmest on average overall 15.5 °C at Rottnest Island
Coolest on average overall 12.7 °C at Bickley
Wettest overall 59.4 mm at Jarrahdale
Driest overall 18.2 mm at Mandurah
Wettest day 13.8 mm at Huntly on the 8th
Strongest wind gust 76 km/h at Ocean Reef on the 4th

Record lowest September total rainfall
New record
(mm)
Old
record
Years of
record
Average for
September
Jandakot Aero 28.6 31.8 in 1977 44 85.4
Perth Metro 35.2 = 35.2 in 2004 26 84.8

Lowest September total rainfall for at least 20 years
Observed
(mm)
Most recent
lower
Average for
September
Pearce RAAF 20.4 7.7 in 1969 68.8
Roleystone 41.7 40.4 in 1974* 112.3
Karragullen North 41.8 0.0 in 1984* 105.9

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




Summary statistics for September 2018
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean for
September
2018
Diff
from
average
Highest for
September
2018
Mean for
September
2018
Diff
from
average
Lowest for
September
2018
Total for
September
2018
Average
for
September
Rank of
September
2018
Fraction of
September
average
Bickley 17.7 +0.2 25.5 22nd 7.7 -0.5 1.4 15th 46.6 124.3 v low 37%
Garden Island HSF 18.1 -0.8 23.2 22nd 11.2 -0.7 6.9 15th 21.4 65.0 v low 33%
Jandakot Aero 20.1 0.0 27.5 22nd 7.3 -0.9 1.9 16th 28.6 85.4 lowest 33%
Mandurah 18.9 -0.1 24.2 22nd 10.9 -0.8 5.9 15th 18.2 64.2 v low 28%
Millendon (Swan Valley) 20.9   28.7 22nd 7.4   1.6 16th 27.4
Pearce RAAF 20.7 +0.6 27.9 23rd 7.8 -1.0 2.5 16th 20.4 68.8 v low 30%
Perth Airport 20.6 +0.4 28.2 22nd 8.1 -0.8 2.6 16th 37.6 72.7 low 52%
Perth Metro 20.5 +0.2 28.0 22nd 8.8 -0.8 2.8 16th 35.2 84.8 lowest 42%
Rottnest Island 18.5 -0.3 23.3 23rd 12.4 -0.5 8.3 15th 18.8 54.6 v low 34%
Swanbourne 19.3 -0.6 25.9 22nd 10.4 -0.6 6.0 15th 37.2 81.5 low 46%

Daily maximum temperatures for September 2018
123456789101112131415161718192021222324252627282930
Bickley16.217.417.015.012.213.314.916.119.717.114.013.114.515.116.217.014.117.219.023.423.325.524.619.318.517.819.320.317.421.0
Garden Island HSF17.518.819.417.714.616.318.218.720.119.515.516.517.615.616.615.515.716.316.319.718.123.221.720.518.818.018.222.616.8
Gosnells City20.020.518.316.419.020.222.318.518.820.419.517.219.720.726.725.728.526.622.121.623.424.2
Jandakot Aero18.519.720.218.615.615.918.219.721.521.117.117.118.317.318.518.616.819.419.325.623.827.526.721.421.121.421.623.718.022.0
Karnet16.717.417.415.015.217.214.514.322.024.719.318.117.718.2
Mandurah17.918.118.817.515.116.518.018.618.919.016.716.717.716.517.517.316.417.917.321.821.324.223.120.620.320.021.023.116.721.5
Millendon (Swan Valley)19.520.320.718.816.416.318.319.922.820.116.316.718.517.818.320.017.320.220.426.226.328.728.422.922.521.921.923.421.723.2
Pearce RAAF18.620.220.518.816.315.819.119.323.320.417.016.918.517.818.519.817.419.620.426.325.427.827.922.121.420.922.023.422.822.3
Perth Airport19.320.020.518.316.215.918.819.622.420.517.316.717.618.219.219.217.419.820.326.425.228.227.521.921.321.722.323.420.122.2
Perth Metro19.220.020.918.915.716.619.120.122.120.716.717.519.117.419.217.817.519.219.826.225.028.026.922.121.520.921.923.619.621.8
Rottnest Island16.918.420.018.115.616.618.419.920.120.216.417.018.216.915.916.716.816.916.321.418.521.723.320.219.918.418.322.017.119.3
Swanbourne18.119.520.118.715.916.519.220.320.720.316.416.818.316.718.616.816.817.817.222.119.525.923.621.220.419.319.923.219.719.3
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 September 2018
123456789101112131415161718192021222324252627282930
Bickley6.95.06.910.66.74.97.29.610.410.26.66.18.48.01.44.85.05.96.87.69.29.311.012.710.67.47.66.78.28.5
Garden Island HSF11.28.29.012.911.28.410.514.113.815.311.710.812.313.66.97.010.29.610.88.913.011.011.613.212.312.410.411.113.212.6
Gosnells City11.25.95.67.59.611.011.310.27.05.23.86.15.36.76.57.010.412.313.98.011.011.013.9
Jandakot Aero7.94.02.610.910.06.18.310.710.69.09.27.511.112.12.81.94.32.24.34.05.66.59.310.25.54.57.910.011.39.4
Karnet3.23.110.26.610.511.09.33.010.09.57.06.86.27.4
Mandurah9.48.58.513.511.08.710.913.514.714.510.710.312.213.15.97.08.68.39.19.012.911.712.414.612.110.69.910.413.511.7
Millendon (Swan Valley)9.93.83.711.09.17.78.19.87.38.39.35.59.511.74.91.64.03.45.94.45.45.38.311.26.94.97.410.311.511.9
Pearce RAAF11.26.34.311.310.07.87.99.47.78.69.95.310.011.35.42.54.72.86.14.05.96.18.512.46.64.48.610.212.512.4
Perth Airport9.16.64.911.09.77.08.210.19.09.89.46.411.012.25.22.64.63.35.76.56.47.810.112.46.85.79.010.610.911.6
Perth Metro10.54.55.110.410.78.39.210.710.49.410.47.411.312.94.92.86.44.67.66.18.78.211.012.68.07.39.310.711.712.0
Rottnest Island11.611.212.313.911.18.711.213.914.614.612.612.111.813.08.310.411.312.012.312.213.913.814.015.314.413.311.411.312.612.6
Swanbourne11.17.07.213.311.28.111.213.611.214.011.510.312.112.86.06.38.67.89.58.210.910.612.013.311.510.010.010.911.411.7
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 September 2018
123456789101112131415161718192021222324252627282930
Anketell - - - 4.0 4.0 - 3.2 1.8 0.8 4.6 0.8 0.2 2.8 - - 1.2 -
Bickley
0.2
7.4 7.6 0.4 2.8 3.4 1.0 8.0 4.2 - 1.2 3.0 - - 1.2 0.2 0.2 0.2 - - - - 0.2
- - 4.4 1.0
Bungendore - - - 4.4 2.6 0.6 2.4 1.4 0.4 2.2 3.2 0.2 0.8 3.2 - 0.2 1.0 - 0.2 0.2 - 0.2 - - - 0.2 - - 2.6 7.4
Chidlow - - - 3.8 3.4 - 3.1 6.0 3.0 4.4 - - 3.0 - 0.2 - - - - - - - - - - - 2.8
Garden Island HSF 0.8 0.2 - 4.6 3.8 0.4 1.2 0.4 0.2 0.2 2.8 - 1.2 2.0 - - 0.2 - - - - - - - 0.6 - - - 0.4 2.4
Gidgegannup - - - 5.8 4.0 0.2 5.8 9.0 1.0 3.2 3.4 - 2.0 4.4 - - 0.8 - - 0.2 - - - - - 0.2 - - 3.0 1.8
Gosnells City - - - 9.1 2.6
0.5 - - - - - - - - - - - - - - - - - -
3.2 3.4
Huntly - - - 4.6 6.8 2.0 4.0 13.8 0.6 1.8 8.0 0.2 0.8 5.8 1.0 - - - - - - - -




1.4 8.2
Jandakot Aero - - - 3.4 5.0 - 2.2 2.8 0.2 2.4 1.2 - 0.8 1.4 - - 1.8 - 0.2 - - - - - - - - - 1.4 5.8
Jarrahdale - 0.2 - 12.0 5.4 0.6 5.0 5.4 2.0 4.0 5.4 0.4 2.0 4.8 - 0.2 1.0 0.2 0.2 0.2 - 0.4 - - 0.6 0.2 0.2 - 1.0 8.0
Karnet
- - 8.8 8.0 6.6 1.8 1.1 0.2 - - - - 0.6 - - -

Karragullen North - - - 6.8 4.6 0.6 1.4 5.4 1.6 4.8 5.6 - 0.8 - - - - - - - - - - - - - - - 7.2 3.0
Maida Vale - - - 10.0 6.4 - 5.0 3.8 0.6 5.0 2.4 0.1 1.0 2.8 - - - 0.8 - 0.2 0.2 - - - 0.2 - - - 4.0 3.8
Mandurah - - - 3.6 2.4 0.4 1.6 2.4 - 0.2 2.8 0.2 0.6 0.4 - - 0.2 0.2 - - - - - - 1.6 - - - - 1.6
Midland - - - 2.4 3.2 - - 22.6 -











Millendon (Swan Valley) - - - 4.4 3.6 0.6 4.6 3.6 0.4 3.4 1.6 - 1.0 0.6 - - 0.8 - - - - - - - 0.2
- - 2.0 0.6
Mosman Park - - - 4.2 4.0 4.2 3.0 10.2 0.4 - 0.6 4.8 0.4 - - 0.2 - 0.4 0.4




Mount Solus - - - 9.0 4.2 0.2 4.8 8.6 1.6 2.2 4.0 - 0.6 3.0 - - 0.6 - 0.2 0.2 0.2 - - - 0.2 0.2 - - 0.8 10.4
Muchea - - - 6.8 9.8 0.2 2.8 1.0 0.2 1.8 8.8 - 0.2 1.2 - - - 0.2 - 0.2 - - 0.2 - 0.2 - - - 0.8 1.0
Mundaring - - - 5.2 6.0 0.2 4.6 7.6 0.8 6.2 7.8 - 1.4 3.0 - - - - - - - - - - - - - - 3.8 1.0
Noble Falls


4.6 5.0 0.4 4.6 5.6 2.0 1.0 3.4
1.8



0.6









3.0 1.0
Pearce RAAF - - - 3.6 5.0 0.6 2.6 0.4 0.8 1.0 2.6 - 0.6 0.8 - - - - 0.2 - - - - - - - 0.2 - 1.4 0.6
Perth Airport - - - 4.0 4.6 1.0 4.0 3.4 - 4.4 1.8 - 0.2 2.4 - - 1.0 - - - - - - - - - - - 3.8 7.0
Perth Metro - - - 5.2 4.2 1.2 4.2 2.6 0.2 5.2 2.6 - 0.8 1.8 - - 0.2 0.2 - - - - - - 0.2 - - - 4.0 2.6
Pinjarra South - - - 4.8 4.4 0.4 3.0 6.4 - 1.2 4.0 - 0.4 1.0 - - 1.0 0.6 - - - - - - 0.4 - - - 0.2 6.8
Roleystone - - - 3.0 4.8 - 3.0 5.0 - 4.6 3.6 - 1.6 2.8 - - - - - - - - - - - - - - 3.2 10.1
Rottnest Island 1.4 - - 0.6 2.4 4.8 0.2 0.4 - 0.4 0.2 - 2.4 1.0 - - 2.4 - - - - - - - - - - - 1.2 1.4
Serpentine - - - 8.6 4.4 0.2 6.2 6.0 1.0 3.2 5.6 - 1.0 2.2 - - 1.4 0.2 - - - - - - 0.6 0.2 - - 0.8 5.6
Swanbourne 0.2 - - 5.0 4.2 2.0 3.0 1.4 1.8 7.0 0.4 - 0.6 4.8 - - 0.4 - - 0.2 - 0.2 - 0.2 0.4 - - - 3.0 2.4
Wanneroo - - - 8.2 5.6 1.2 4.4 6.0 8.0 - 1.0 1.6















Werribee - - - 2.6 4.0 - 2.4 4.2 1.4 0.8 2.4 - 1.0 0.6 - - - 0.2 - 0.2 - - - - - 0.2 - - 1.8 1.2
Whiteman Park - - - 4.4 2.6 0.8 5.6 3.4 0.4 3.2 2.6 - 1.4 1.2 - - 0.6












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.

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 1 October 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