Perth in August 2012: A relatively warm month with a wet start

  • Rainfall: near average to below average
  • Maximum temperature: average to above average
  • Minimum temperature: near average

Rainfall

August rainfall totals across the Perth metropolitan area were generally close to average, though totals were below average in some southern suburbs and at Perth Metro. Rainfall totals for the month mostly ranged from 80 mm to 120 mm, though Bickley in the hills reported over 170 mm.

Light to moderate rainfall was registered for the first eight days of August 2012 across Perth with a persistent westerly flow and a number of cold fronts moving over the region. A strong cold front and pre-frontal trough brought moderate to heavy falls to the Perth area on the 12th and Mundaring in the hills received 53 mm in 24 hours to 9am on the 13th, the highest daily total for the month in the Perth metropolitan area. A weak cold front produced light rainfall across Perth on the 14th, whilst a trough and a cold front moved through southwest WA on the 21st, resulting in light to moderate rainfall across the Perth area. A weak cold front and subsequent westerly flow produced mainly light rainfall on the 27th to 29th, while another cold front crossed through Perth during the 31st.

Perth Metro recorded 87.2 mm of rainfall on 16 rain days in August 2012, which was below average. In combination with its driest July last month in 137 years of record, and a very much below average May, Perth Metro recorded its 5th driest January to August period on record with 423.4 mm on 67 rain days. Perth Metro's driest January to August period was in 2006 when 340.4 mm was recorded, whilst in 2010 Perth Metro recorded its 4th driest January to August period.

Maximum temperature

Mean maximum temperatures in August 2012 were above average at Perth Metro, Perth Airport and Pearce RAAF, whilst remaining sites were near average, with most sites observing mean daily maxima in the 18 °C to 20 °C range.

With the exception of Bickley in the hills, cool (mid-to-high teens) to mild (low twenties) days were experienced throughout August for most of sites in the Perth metropolitan area. The coolest day for most locations was the 13th, with daily maxima below 17 °C across Perth due to a cold southerly flow in the wake of a cold front. Warm days were experienced on the 10th and 11th, and again on the 18th, 20th, and 25th, with daily maxima above 20 °C across the metropolitan area as a result of strong high pressure systems in the Bight directing warm northerly winds over the region.

Perth Metro's mean daily maximum temperature in August 2012 was 20.1 °C, which was 1.2 °C above the average, and equal fourth highest on record. A mean maximum of 20.1 °C in August had also been recorded in 1978, whilst the highest mean maximum for August since observations commenced in 1897 was 20.3 °C in 1902. Daily maxima ranged from a cool 16.0 °C on the 13th to a mild 24.5 °C on the 11th, with 15 days during the month recording 20.0 °C or more. This equalled 15 days with a maximum temperature of 20.0 °C or greater recorded in 2006 and 2011, and was only lower than the 18 such days recorded in 1902.

For the January to August period, Perth Metro has observed a mean maximum temperature of 25.6 °C which is the second highest on record behind the 25.9 °C observed in January to August 2011.

Minimum temperature

Mean minimum temperatures in August 2012 were near average for all sites in the Perth metropolitan area, with mean minima generally in the 8 °C to 10 °C range, while Rottnest Island and Garden Island saw average overnight temperatures above 10 °C.

Mild to warm nights with daily minima above 10 °C for many sites were registered on the 3rd to 4th, 6th to 7th, 12th, 20th to 22nd, and 28th. The 21st saw daily minima generally between 14 °C and 16 °C across the Perth area, and was the warmest night of the month for most sites. Cold nights were observed for many sites on the 8th and 9th, 16th, 19th, 23rd, and 26th, as a result of generally clear skies and light winds. Most sites recorded their coldest night of the month on the 8th or 9th, though the lowest temperature recorded in the metrolpolitan area in August was 1.4 °C at Jandakot Aerodrome on the 16th.

Perth Metro's mean daily minimum temperature in August was 8.6 °C, 0.5 °C above the August average of 8.1 °C. Perth Metro recorded a total of four cold nights (a cold night at Perth Metro is a minimum of less than 5 °C) in August, the least number of cold nights for August for six years, since four cold nights were recorded in 2006. Perth Metro minima ranged from a cold 2.9 °C on the 9th to a warm 15.3 °C on the 21st.

Sunshine

Perth recorded an average daily sunshine of 7.5 hours in August 2012, which is close to the August average of 7.2 hours.

Further information

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Extremes in August 2012
Hottest day 25.0 °C at Gosnells City on the 10th
Warmest days on average 20.3 °C at Gosnells City
Coolest days on average 16.8 °C at Bickley
Coldest day 13.3 °C at Bickley on the 2nd
13.3 °C at Bickley on the 13th
Coldest night 1.4 °C at Jandakot Aero on the 16th
Coolest nights on average 7.1 °C at Jandakot Aero
Warmest nights on average 12.9 °C at Rottnest Island
10.2 °C at Swanbourne
Warmest night 16.6 °C at Rottnest Island on the 12th
15.9 °C at Swanbourne on the 21st
Wettest overall 182.6 mm at Mundaring
Wettest day 53.0 mm at Mundaring on the 13th
Highest wind gust 80 km/h at Bickley on the 12th
80 km/h at Rottnest Island on the 12th

Summary statistics for August 2012
Maximum temperatures
for August
(°C)
Minimum temperatures
for August
(°C)
Rainfall
for August
(millimetres)
Mean for
August
2012
Diff
from
average
Highest for
August
2012
Mean for
August
2012
Diff
from
average
Lowest for
August
2012
Total for
August
2012
Average
for
August
Rank of
August
2012
Fraction of
August
average
Bickley 16.8 +0.9 21.6 11th 8.2 +0.8 4.3 9th 173.2 169.6 average 102%
Champion Lakes 19.1   23.5 10th 9.8   4.9 23rd 105.8
Garden Island HSF 18.4 +0.4 20.8 30th 11.3 +0.3 7.5 8th 87.2 88.2 average 99%
Gosnells City 20.3 +1.1 25.0 11th 9.1 +0.3 5.1 8th 99.5 125.6 low 79%
Jandakot Aero 19.6 +1.1 24.3 10th 7.1 +0.2 1.4 16th 100.6 124.6 low 81%
Medina Research Centre 19.8 +1.1 24.5 10th 8.5 +0.5 3.8 9th 94.2 114.2 low 82%
Pearce RAAF 19.8 +1.5 24.3 11th 7.9 -0.2 2.6 9th 81.8 103.9 low 79%
Perth Airport 20.0 +1.5 24.5 11th 8.2 +0.2 2.7 16th 111.4 117.2 average 95%
Perth Metro* 20.1 +1.2 24.5 11th 8.6 +0.5 2.9 9th 87.2 133.4 low 65%
Rottnest Island 18.7 +1.0 20.8 30th 12.9 +0.6 10.2 8th 93.6 99.3 average 94%
Swanbourne 19.9 +1.2 24.6 10th 10.2 +0.3 5.8 9th 120.0 113.0 average 106%

Daily maximum temperature
Central Coast (09)12345678910111213141516171819202122232425262728293031
Bickley13.413.316.516.316.218.314.215.316.820.421.615.813.314.314.916.415.720.619.020.115.913.415.317.420.317.915.716.317.119.620.0
Champion Lakes15.717.118.218.518.420.216.417.619.923.523.317.715.117.416.717.919.723.318.722.419.115.716.819.922.519.119.518.619.222.121.3
Garden Island HSF16.817.717.719.018.720.016.916.919.320.219.618.316.018.015.915.519.520.517.520.219.415.616.619.718.519.318.818.618.720.820.6
Gosnells City16.817.819.020.020.021.317.821.225.025.018.116.318.019.720.024.520.423.920.216.417.822.023.721.219.619.921.023.0
Jandakot Aero16.518.218.619.519.520.817.217.720.024.323.318.415.918.217.518.619.723.419.022.720.316.317.619.422.620.119.120.019.622.921.9
Medina Research Centre16.918.718.919.619.520.517.318.420.924.522.418.016.018.517.618.620.523.519.022.420.016.018.520.023.219.820.619.020.023.221.6
Pearce RAAF17.518.219.419.419.621.917.918.219.722.224.319.316.118.117.418.820.223.821.123.220.516.317.819.523.420.717.919.220.622.6
Perth Airport16.018.119.219.320.221.617.118.320.223.224.518.216.418.318.219.419.423.820.923.719.917.018.220.423.221.018.819.120.122.922.1
Perth Metro16.818.419.319.719.721.717.918.220.223.424.518.816.019.118.018.920.024.120.923.820.416.418.821.023.420.319.519.420.522.921.7
Rottnest Island17.117.518.019.719.220.617.017.119.319.720.619.216.118.216.215.619.620.018.820.019.416.217.020.020.419.817.718.919.920.820.6
Swanbourne16.818.119.119.919.620.817.717.920.524.621.818.016.719.018.118.820.823.720.522.120.116.918.221.023.220.119.118.820.122.421.0

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 minimum temperature
Central Coast (09)12345678910111213141516171819202122232425262728293031
Bickley6.87.39.59.87.99.39.55.64.35.79.112.35.57.57.75.47.15.89.310.612.78.55.87.87.410.59.19.68.87.310.6
Champion Lakes8.38.111.911.68.912.212.65.27.38.812.113.98.410.010.76.09.39.66.812.715.512.14.98.611.27.29.411.59.49.310.4
Garden Island HSF13.410.012.314.111.013.413.77.58.38.910.014.810.711.411.910.511.09.78.613.816.012.48.711.610.09.012.012.711.810.410.5
Gosnells City8.07.911.711.08.59.312.75.18.59.09.58.410.310.15.210.05.510.115.212.35.18.09.56.48.411.59.47.5
Jandakot Aero6.77.410.810.56.511.113.23.61.75.04.611.77.39.89.01.47.63.22.510.514.812.02.27.75.53.15.210.77.73.14.2
Medina Research Centre10.57.611.513.78.512.313.45.23.85.06.512.07.910.410.04.48.05.53.812.014.612.13.89.75.94.77.612.38.65.06.1
Pearce RAAF5.85.610.110.37.611.512.34.02.66.45.213.47.69.99.42.77.79.84.810.314.511.83.09.98.04.25.710.67.94.77.0
Perth Airport7.36.310.89.97.111.412.34.36.25.87.513.97.08.68.82.79.18.94.112.414.511.84.08.56.74.97.210.57.46.98.9
Perth Metro8.57.611.211.08.912.412.76.02.94.77.513.57.19.410.43.610.06.45.411.515.313.34.79.46.85.88.010.69.06.08.0
Rottnest Island11.911.412.813.613.014.013.210.211.512.114.116.611.511.913.112.311.811.613.314.916.112.411.012.012.314.214.012.814.312.614.7
Swanbourne12.38.611.713.610.712.812.77.55.87.510.514.28.310.510.87.19.18.68.512.415.912.76.310.28.78.910.211.310.48.410.4

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 25.4 6.8 14.0 8.6 1.6 1.2 28.0 1.8 0.4 - - 0.4 44.6 0.2 5.0 0.4 - 0.2 - - 11.0 16.8 0.4 0.2 - - - 3.4 2.4 0.4 -
Champion Lakes 14.2 6.8 13.0 8.0 - 1.6 17.2 1.4 - - - - 24.4 0.4 3.6 0.2 - - - - 1.6 10.0 - 0.2 - - - 2.8 0.2 0.2 -
Garden Island HSF 5.0 12.0 8.4 5.8 - 0.8 19.2 3.2 - - - 1.2 14.0 0.4 1.8 0.2 - - - - 4.0 3.0 0.6 3.0 - - - 2.8 1.4 0.2 0.2
Gosnells City 12.1 6.8 11.8 5.8 1.4 0.8 20.8 3.8 »» »» »» »» »» »» 1.0 - - - - - 4.8 5.6 0.2 - - - - 2.8 0.8 -
Jandakot Aero 10.6 6.6 14.0 3.4 0.2 5.0 13.2 4.6 - - - 0.6 24.0 1.4 2.2 - - - - - 2.6 11.0 - - - - - 1.0 0.2 - -
Jarrahdale 9.2 10.6 9.0 5.6 1.0 3.0 32.6 1.2 0.2 0.4 0.2 1.0 28.8 0.6 2.8 0.2 0.2 - 0.2 0.2 7.8 17.6 - 0.2 - 0.4 0.4 5.2 2.0 0.4 0.2
Medina Research Centre 8.4 9.4 17.4 2.8 - 4.2 11.4 1.8 - - - 1.2 14.2 2.8 4.2 - - - - - 3.4 8.4 0.4 - - - - 2.0 2.0 0.2 -
Mundaring 23.2 8.6 12.4 4.0 1.0 1.6 22.2 2.6 0.8

0.4 53.0 1.2 6.4 0.2
0.2

14.8 30.0








Pearce RAAF 3.0 7.0 7.6 7.4 1.8 1.8 12.4 2.4 - - - 0.2 18.6 - 3.8 - - - - - 4.2 5.8 0.2 - - - - 1.2 4.2 0.2 -
Perth Airport 16.6 9.2 11.2 3.4 0.2 0.4 11.8 2.2 - - - - 22.4 0.2 3.6 - - - - - 5.8 12.0 0.2 - - - - 10.2 2.0 - -
Perth Metro 11.2 7.8 9.8 1.8 1.0 0.6 9.6 4.2 - - - 0.2 19.2 0.6 1.4 - - - - - 2.8 7.6 - - - - - 6.6 2.8 - -
Roleystone 16.4 7.8 16.0 9.4 1.0 1.4 25.4




34.0 0.6 2.8




5.8 16.2 0.4



3.8 3.2

Rottnest Island 3.0 4.4 16.8 5.6 8.6 1.2 13.2 9.6 - - - 0.6 10.8 1.2 5.4 - - - - - 1.0 1.6 0.2 2.0 - - 2.6 5.8 - - -
Serpentine 7.6 8.8 7.2 3.0 0.2 6.8 21.4 2.4 0.2 - - 0.8 17.2 0.4 1.4 - - - - - 5.2 9.2 - 0.2 - - - 5.4 0.8 - -
Swanbourne 9.2 24.4 12.6 2.2 2.8 1.4 12.8 5.4 0.2 - - 0.4 17.0 2.4 6.8 - - - - - 3.2 5.4 0.4 - - - 0.2 10.4 2.6 0.2 -

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 11 am on Monday 3 September 2012. 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.
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