Perth in August 2011: A warm month

  • Rainfall: Mostly near average.
  • Maximum temperature: Highest on record at several sites.
  • Minimum temperature: Above average.

Rainfall

Rainfall across the Perth metropolitan area during August 2011 was generally near average apart from Bickley which observed very much above average rainfall for the month.

Strong westerly flow across the south of WA, with embedded cold fronts, brought wet weather to Perth during the beginning of August. Further cold fronts crossed southwest WA during the middle of the month resulting in moderate rainfall across the Perth metropolitan area. On the 13th, Rottnest Island observed severe wind gusts and some damage was reported near Como, while gusty winds ahead of a cold front on the 15th resulted in minor roof damage and fallen trees across parts of Perth. Another strong front moved across Perth on the 21st and 22nd, with heavy rainfall observed at a number of locations. Mundaring observed 59.2 mm in the 24 hours to 9am on the 22nd, which was the heaviest daily total for the month in the Perth metropolitan area, while Jarrahdale observed 54.8 mm and Bickley 52.6 mm on the same day. Minor roof, ceiling and flood damage was reported in several suburbs.

Perth Metro recorded 115.2 mm of rainfall on 17 rain days in August 2011, which is close to the long term average of 133.6 mm on 15.6 rain days. Historically, August rainfall extremes range from 11.8 mm in 1978 to 318.3 mm in 1945, while last August (2010), Perth Metro recorded 63.0 mm on 8 rain days. The last time Perth Metro exceeded the August average was in 2004 when 175.6 mm of rainfall fell on 21 rain days.

So far this year (January to August), Perth Metro has recorded 582.6 mm of rainfall on 70 rain days, which is more than was received for the whole of 2010 (503.8 mm on 65 rain days). However, Perth rainfall to date is below the average for the 8 month period of 682.3 mm on 74.8 rain days.

Maximum temperature

Averaged over August 2011, mean daily maximum temperatures were above to very much above average with most sites between 1.0 °C and 2.0 °C above average. Jandakot Aerodrome, Swanbourne and Gosnells City observed their warmest August on record. Apart from a few cool days towards the beginning of the month, daily maximum across Perth during August 2011 were generally near to or above average, with very much warmer than normal conditions experienced in the days prior to cold fronts on the 13th and 21st.

Perth Metro's mean daily maximum temperature in August was 20.2°C, the equal second warmest August on record with 2006, only below 20.3 °C recorded in 1902 . The average for August is 18.8°C. Daily maxima ranged from a mild 16.5°C on the 5th to warm 26.3°C on the 21st, which was Perth Metro's warmest August day for 5 years.

Perth Metro's mean daily maximum temperature for the January to August period was 25.9 °C, which was the warmest start to a year since records commenced in 1897. The previous record was 25.4 °C in 1978, while the average for January to August is 24.5 °C.

Minimum temperature

Minimum temperatures across Perth during August 2011 were near to or above average, with most sites between 0.5 °C and 1.5 °C above normal. Cold overnight temperatures (less than 5 °C) were observed at most sites during the early part of the month, when Jandakot Aerodrome observed the coldest night for August 2011 in metropolitan Perth with 2.5 °C on the 4th, and towards the end of the month. Jandakot observed the coolest nights on average with a mean daily minimum temperature of 8.1 °C, while Rottnest Island was the warmest with 13.3°C.

Perth Metro's mean daily minimum temperature in August was 9.1 °C, above the August average of 8.1 °C. Daily minima ranged from a cold 3.9°C on the 5th to a mild 14.3°C on the 22nd at Perth Metro.

Wind and Sunshine

Rottnest Island observed the strongest wind gust for the month on the 21st when 104 km/h was observed, closely followed by 98 km/h at Swanbourne on the same day as a strong cold front crossed Perth.

Perth recorded an average daily sunshine of 8.1 hours in August, which was the 4th sunniest August on record and the sunniest since the record of 8.5 hours in 2008. The average sunshine hours for August is 7.1 hours per day.

Further information

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Extremes in August 2011
Hottest day 27.5 °C at Gosnells City on the 21st
Warmest days on average 20.8 °C at Gosnells City
Coolest days on average 16.9 °C at Bickley
Coldest day 13.2 °C at Bickley on the 5th
Coldest night 2.5 °C at Jandakot Aero on the 4th
Coolest nights on average 8.1 °C at Jandakot Aero
Warmest nights on average 13.3 °C at Rottnest Island
Warmest night 17.3 °C at Rottnest Island on the 21st
Wettest overall 223.4 mm at Mundaring
Wettest day 59.2 mm at Mundaring on the 22nd
Highest wind gust 104 km/h at Rottnest Island on the 21st

Record highest August mean daily maximum temperature
Mean daily maximum
temperature
for August 2011 (°C)
Previous highest
for August
Years of
record
Average for
August
Jandakot Aero 20.1 19.8 in 2006 21 18.4
Gosnells City 20.8 20.6 in 2006 18 19.2
Swanbourne 20.0 19.9 in 2006 17 18.6



Summary statistics for August 2011
Maximum temperatures
for August
(°C)
Minimum temperatures
for August
(°C)
Rainfall
for August
(millimetres)
Mean for
August
2011
Diff
from
average
Highest for
August
2011
Mean for
August
2011
Diff
from
average
Lowest for
August
2011
Total for
August
2011
Average
for
August
Rank of
August
2011
Fraction of
August
average
Bickley 16.9 +1.1 23.2 21st 8.3 +0.9 3.0 5th 205.8 169.5 high 121%
Champion Lakes 19.2   25.3 21st 10.3   6.2 4th 54.8
Garden Island HSF 18.7   24.1 21st 12.0   8.4 5th 71.6 88.3 low 81%
Gosnells City 20.8 +1.6 27.5 21st     4.9 4th 125.7 126.1 average 100%
Jandakot Aero 20.1 +1.7 26.2 21st 8.1 +1.3 2.5 4th 136.2 125.3 average 109%
Medina Research Centre 20.4 +1.7 25.4 21st 10.1 +2.1 4.1 4th 96.6 114.9 low 84%
Pearce RAAF 19.7 +1.5 25.6 21st 8.8 +0.7 3.7 26th 60.2 103.6 v low 58%
Perth Airport 20.2 +1.8 27.0 21st 8.8 +0.8 3.0 4th 128.6 117.3 average 110%
Perth Metro 20.2 +1.4 26.3 21st 9.1 +1.1 3.9 5th 115.2 133.6 average 86%
Rottnest Island 18.7 +1.0 22.5 21st 13.3 +1.1 9.9 5th 58.8 99.3 low 59%
Swanbourne 20.0 +1.4 24.5 21st 10.9 +1.1 5.1 5th 106.2 112.6 low 94%

Daily maximum temperature
Central Coast (09)12345678910111213141516171819202122232425262728293031
Bickley15.115.914.314.213.216.617.815.015.216.616.318.420.915.716.313.415.316.620.721.023.215.617.814.915.016.017.818.519.718.019.5
Champion Lakes18.719.716.716.116.119.519.518.217.519.219.221.623.117.619.616.017.519.122.422.325.317.319.517.017.717.418.821.022.019.820.9
Garden Island HSF19.520.017.215.216.619.719.618.417.218.619.319.521.917.919.016.117.719.121.621.324.117.719.416.816.917.218.218.219.5
Gosnells City19.520.618.217.217.521.021.319.420.020.222.825.219.020.417.419.521.224.525.627.519.021.518.219.718.520.522.223.720.5
Jandakot Aero20.021.017.816.316.720.420.319.117.819.219.821.324.318.420.117.218.519.823.623.026.218.220.318.318.319.820.822.621.121.6
Medina Research Centre20.820.718.016.917.320.420.119.417.920.020.021.924.518.820.516.819.021.024.023.125.418.121.123.020.9
Pearce RAAF20.220.217.516.115.619.920.918.617.918.418.521.723.618.519.716.517.719.022.523.825.618.220.317.517.718.019.520.722.621.121.4
Perth Airport19.820.217.316.916.520.520.819.418.719.520.222.024.718.420.317.418.319.723.424.127.018.320.918.118.618.420.121.022.819.821.7
Perth Metro20.120.518.016.616.320.320.819.519.019.419.422.124.618.920.017.718.519.623.923.526.319.020.917.919.018.219.620.722.420.122.2
Rottnest Island19.519.917.315.415.919.819.619.017.918.419.519.221.218.118.916.816.918.820.221.022.517.619.017.216.416.818.718.020.519.619.5
Swanbourne19.920.218.017.416.620.620.219.819.320.520.923.519.019.917.918.622.622.124.518.320.318.218.918.919.220.823.220.420.6

This table is very wide; you may have to scroll sideways to see all the days, and you may need to set the paper to 'landscape' to print.
The temperatures in this table are coloured by
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 difference from average


Daily minimum temperature
Central Coast (09)12345678910111213141516171819202122232425262728293031
Bickley10.212.88.85.33.03.98.111.77.76.85.76.09.610.69.76.77.28.26.011.911.711.56.68.35.46.06.58.28.011.811.9
Champion Lakes12.514.511.06.26.58.112.614.28.77.58.49.812.213.011.49.88.29.49.212.215.414.08.510.96.96.56.58.49.614.312.2
Garden Island HSF14.815.315.09.58.49.713.214.914.58.89.610.411.813.213.611.910.710.710.213.916.114.711.314.210.38.99.412.111.6
Gosnells City11.613.710.84.95.16.510.514.25.86.88.410.111.711.810.38.48.215.55.06.58.513.411.8
Jandakot Aero10.712.812.62.53.96.412.213.06.52.84.95.38.813.08.010.77.16.44.811.213.914.15.612.03.34.03.44.84.512.89.9
Medina Research Centre13.715.013.04.14.65.112.713.48.24.45.67.19.613.412.110.18.47.49.012.515.714.37.413.112.99.6
Pearce RAAF12.013.810.95.04.18.411.012.69.64.25.69.711.312.111.09.28.17.99.711.613.814.37.610.54.63.74.64.96.74.610.8
Perth Airport11.213.612.03.04.65.911.013.28.44.15.77.310.313.310.79.97.58.19.59.014.413.97.312.04.44.44.44.96.412.210.8
Perth Metro11.314.212.24.93.94.711.313.38.74.44.37.411.213.610.511.58.38.35.711.314.114.37.812.95.34.64.66.16.512.810.9
Rottnest Island14.014.512.512.09.911.113.315.114.211.412.611.814.513.614.711.211.413.013.316.017.314.513.313.412.112.112.213.512.914.515.3
Swanbourne13.314.913.17.55.16.312.115.511.17.46.99.112.813.512.810.49.010.89.513.715.214.49.313.39.86.97.58.78.016.013.0

This table is very wide; you may have to scroll sideways to see all the days, and you may need to set the paper to 'landscape' to print.
The temperatures in this table are coloured by
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 difference from average


Daily rainfall
Central Coast (09)12345678910111213141516171819202122232425262728293031
Bickley 11.8 35.8 14.0 7.4 0.2 - 3.8 0.2 5.8 0.2 - - - 29.0 6.6 20.6 1.0 - - - - 52.6 0.4 15.8 - - - - - 0.2 0.4
Champion Lakes 8.6 4.4 0.2 0.2 - - 0.6 - 1.6 - - - - 25.6 2.8 5.2 - - - - - 5.2 0.4 - - - - - - - -
Garden Island HSF 2.4 4.6 5.2 6.0 0.2 - 1.4 - 6.0 0.2 - - - 16.0 0.4 5.8 2.8 - - - - 17.4 0.4 2.8 - - - - -

Gosnells City 9.7 12.4 5.8 4.5 - - 2.0 2.0 »» 3.3 - - - 19.2 1.4 12.6 - - - - - 40.0 0.4 6.2 - - - - - 1.6 4.6
Jandakot Aero 5.8 7.0 11.0 4.6 - - 1.0 - 4.4 - - - - 27.2 0.4 11.6 0.6 - - - - 46.4 0.4 12.2 -
- - - - 3.6
Jarrahdale 6.0 21.8 19.0 6.4 - 0.2 1.2 0.2 7.2 0.2 - 0.2 - 34.2 2.6 24.4 1.8 - 0.4 - 0.4 54.8 0.6 11.6 0.2 0.4 - 0.2 - 0.2 -
Medina Research Centre 2.9 6.6 4.4 8.2 - - 0.8 0.4 4.8 - - - - 23.8 0.4 8.6 0.4 - - - 4.7 29.8 0.4 4.7




- 0.4
Mundaring 18.2 33.6 20.0 9.4

2.6 1.2 6.2 0.2

0.2 18.2 8.0 20.8 2.8

0.2 0.2 59.2 2.0 13.8 0.2

0.2 0.2 2.2 3.8
Pearce RAAF 5.8 16.2 7.2 3.8 -
5.8 -
0.2
-


17.8 0.4 - - - -
1.0 2.0 -
- - - - -
Perth Airport 8.6 15.4 9.4 6.4 - - 1.6 0.6 2.0 0.2 - - - 16.8 5.4 13.6 0.6 - - - - 37.0 0.4 8.4 - - - - - 0.2 2.0
Perth Metro 6.2 16.2 6.4 4.6 - - 3.0 0.8 2.8 - - - - 18.0 2.8 7.8 0.8 - - - - 38.6 0.2 4.6 0.2 - - - - 0.8 1.4
Roleystone 13.0 10.2 13.6 6.8



4.0



28.2 2.2 16.0 1.0













Rottnest Island 1.2 4.8 1.4 0.8 - - 0.2 - 1.6 - - - - 23.0 - 2.8 1.6 0.2 - - - 16.4 0.4 3.6 - - - - - - 0.8
Serpentine 4.0 15.4 9.0 4.0 0.2 - 0.6 0.2 11.6 0.2 - - - 20.4 1.0 18.6 0.6 0.2 - - - 30.8 0.2 5.8 0.2 - - - - - -
Swanbourne 7.4 10.8 4.6 3.4 0.2 - 1.6 - 0.4 0.2 - - - 11.8 0.4 11.0 3.0 - - - 0.2 41.6 - 2.4 - - - - - 0.4 6.8

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 marked like this 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).
This table is very wide; you may have to scroll sideways to see all the days, and you may need to set the paper to 'landscape' to print.


Notes

A Monthly Climate Summary is prepared to list the main features of the weather in Perth using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.

This statement has been prepared based on information available at 10 am on Thursday 1 September 2011. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

Averages 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.

Records in this summary are based on sites with at least 10 years of data.

*Official Perth observations have been recorded at several different sites with varying instrumentation over the years, and these changes can affect the continuity of the climate record. For the current Mt Lawley site, the most significant changes of this kind relate to minimum temperature and rain days.

For that reason, current mean temperature and rain-day data quoted here are based only on readings from the Mt Lawley site, which commenced observations in 1993. Sunshine recordings are from Perth Airport and for similar reasons current means use only Perth Airport data, which commenced in 1993.

For PDF files of Perth Metro climate statistics for other months, please click here for extremes and here for averages.

Further information

Media
(03) 9669 4057
Enquiries