Perth in July 2011: An average July

  • Rainfall: Near average to above average for Perth.
  • Maximum temperature: Near average across Perth.
  • Minimum temperature: Near average across Perth.

Rainfall

Rainfall in July 2011 was near average for most Perth Metropolitan sites, though it was above average on Rottnest and Garden Island, as well as in the hills, with monthly rainfall totals across the metropolitan area generally in the 120-220 mm range.

A pre-frontal trough and cold front, followed by unstable westerly winds produced persistent rainfall from 30 June to 3 July, with daily rainfall totals of 20 to 40 mm recorded in the Perth metropolitan area in the 24 hours to 9 am on 1 July. A cloudband over the region on the 10th and 11th brought mainly light rainfall, with some isolated moderate falls to the Perth area, whilst a cold front on the 15th brought further moderate falls. After a short break, several cold fronts produced light to moderate rainfall between the 20th and 26th, though Rottnest Island received an exceptionally heavy fall from a thunderstorm with daily total of 66.8 mm on the 21st, the third highest July daily rainfall recorded at Rottnest Island, and the highest daily total in the Perth area for the month. Flash flooding occurred at Fremantal on the 22nd. Several cold fronts and a low pressure system produced more downpours and windy weather at the last few days of July.

Perth Metro recorded 161.0 mm of rainfall on 18 days during July 2011, which was near average. Despite this, the total rainfall for the seven months from January to July 2011 at Perth Metro remained below average, with 467.4 mm recorded on 53 rain days. The long-term average for this period is 548.7 mm on about 59 days, while the total for the same period last year was 347.6 mm on 38 days.

Maximum temperature

Daytime temperatures during July 2011 were near average across the Perth metropolitan area. Mean daily maximum temperatures were in the 15 to 19 °C range, and generally within 0.5 °C of long-term means. The warmest day of the month was the 14th as Gosnells City recorded the highest daily maximum in the Perth metropolitan area for July 2011 with 22.8 °C. The coldest day of the month was the 11th when Bickley registered a daily maximum temperature of 9.6 °C, which was the coldest July day in 18 years of record.

Perth Metro's mean maximum temperature in July 2011 was 18.3 °C, which is the same as the long-term average. Daily maxima ranged from a cold 13.0 °C on the 11th, to a mild 22.0 °C on the 14th.

Minimum temperature

Overnight temperatures during July 2011 were near average across the Perth area. Mean daily minimum temperatures were in the 8 to 12 °C range, and generally within 1 °C of normal. The coldest night of the month for many sites was the 4th, with several sites registering daily minimum temperatures 5 °C or lower, and Jandakot Aerodrome recorded the lowest minimum in Perth in July 2011 with -0.4 °C. The warmest night of the month for the Perth area was the 31st, and Jandakot Aerodrome recorded the warmest July night in 22 years of record.

Perth Metro's mean minimum temperature in July was 8.5 °C, which is near the average of 7.8 °C. Minima at Perth Metro ranged from a cold 1.3 °C on the 4th, to a mild 15.4 °C on the 31st, the highest overnight minimum for July at Perth Metro in 10 years, since 15.4 °C was recorded on 30 July 2001.

Wind and sunshine

Cold fronts brought significant winds to the Perth metropolitan area in the second half of July, with a tornado reported at Serpentine on the 22nd with the passage of a cold front. Severe wind gusts were observed at Rottnest Island on the 27th and the 31st, with the highest wind gust of 126 km/h from the northwest at 1713 WST on the 27th when a strong cold front crossed the Perth region. This gust was the strongest reported in the metropolitan area in July 2011. Significant roof damage was reported at Rockingham with minor damage also reported in Kalamunda.

Perth recorded an average daily sunshine of 5.2 hours in July 2011, which is the least sunshine hours for Perth in July for three years, since 5.1 hours per day was recorded in 2008. The average sunshine for Perth in July is 6.1 hours per day.

Further information

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Extremes in July 2011
Hottest day 22.8 °C at Gosnells City on the 14th
Warmest days on average 18.8 °C at Gosnells City
Coolest days on average 15.0 °C at Bickley
Coldest day 9.6 °C at Bickley on the 11th
Coldest night -0.4 °C at Jandakot Aero on the 4th
Coolest nights on average 7.5 °C at Jandakot Aero
Warmest nights on average 12.3 °C at Rottnest Island
9.9 °C at Swanbourne
Warmest night 16.3 °C at Rottnest Island on the 25th
15.4°C at Perth Metro on the 31st
Wettest overall 270.0 mm at Bickley
Wettest day

66.8 mm at Rottnest Island on the 21st
42.3 mm at Pickering Brook on the 31st

Highest wind gust 126 km/h at Rottnest Island on the 27th




Record lowest July daily maximum temperature
Lowest daily maximum
temperature
in July 2011 (°C)
Previous lowest
for July
Years of
record
Average for
July
Bickley 9.6 on the 11th 9.8 on the 9th in 2010 18 15.0



Record highest July daily minimum temperature
Highest daily minimum
temperature
in July 2011 (°C)
Previous highest
for July
Years of
record
Average for
July
Jandakot Aero 15.1 on the 31st 15.0 on the 3rd in 1994 22 6.8



Summary statistics for July 2011
Maximum temperatures
for July
(°C)
Minimum temperatures
for July
(°C)
Rainfall
for July
(millimetres)
Mean for
July
2011
Diff
from
average
Highest for
July
2011
Mean for
July
2011
Diff
from
average
Lowest for
July
2011
Total for
July
2011
Average
for
July
Rank of
July
2011
Fraction of
July
average
Bickley 15.0 0.0 18.7 14th 7.8 +0.7 3.9 4th 270.0 221.8 high 122%
Champion Lakes 17.5   21.1 14th 9.8   3.8 4th 143.6
Garden Island HSF 17.5   20.4 24th 11.5   7.4 4th 175.6 121.8 high 144%
Gosnells City 18.8 +0.2 22.8 14th         137.0 164.5 low 83%
Jandakot Aero 18.2 +0.4 22.3 24th 7.5 +0.7 -0.4 4th 181.0 178.3 average 102%
Medina Research Centre 18.0 -0.2 22.5 24th 8.9 +0.6 1.3 4th        
Pearce RAAF 17.6 -0.2 21.9 24th 8.7 +0.2 0.7 4th        
Perth Airport 18.4 +0.5 22.1 14th 8.6 +0.6 0.2 4th 160.2 159.1 average 101%
Perth Metro 18.3 0.0 22.0 14th 8.5 +0.7 1.3 4th 161.0 169.7 average 95%
Rottnest Island 17.3 -0.4 21.2 24th 12.3 0.0 9.2 3rd 181.6 143.9 high 126%
Swanbourne 18.2 -0.1 21.8 14th 9.9 +0.3 4.7 4th 155.2 151.5 average 102%

Daily maximum temperature
Central Coast (09)12345678910111213141516171819202122232425262728293031
Bickley13.913.111.913.313.114.011.613.712.710.79.613.416.218.715.115.615.416.016.216.217.115.515.818.516.917.218.616.015.416.416.8
Champion Lakes16.416.014.215.315.816.214.215.615.414.112.916.419.921.117.817.717.818.119.018.118.316.318.220.919.419.220.519.219.019.419.4
Garden Island HSF17.316.514.115.114.615.415.117.016.915.313.616.718.720.318.716.718.619.118.217.117.617.116.920.418.119.419.919.419.219.919.3
Gosnells City17.517.015.116.117.117.315.417.116.514.417.820.522.818.218.719.220.219.419.220.422.419.421.022.020.520.021.020.9
Jandakot Aero17.916.914.815.616.117.015.417.116.114.212.817.420.221.919.217.918.818.819.719.319.117.219.122.318.619.721.520.019.920.620.4
Medina Research Centre17.216.714.915.616.116.814.517.916.014.912.817.120.722.419.018.619.519.720.218.019.717.617.822.517.919.321.520.4
Pearce RAAF17.415.714.415.015.816.514.916.315.812.813.216.919.121.317.718.217.417.618.718.918.018.219.021.919.319.919.220.720.4
Perth Airport17.416.914.915.916.417.316.016.316.514.112.817.120.022.118.718.918.819.220.218.618.918.719.821.718.620.321.820.120.420.920.7
Perth Metro17.216.714.315.416.416.415.316.616.614.013.017.019.922.019.118.418.819.119.918.319.818.719.921.718.820.521.420.320.521.021.1
Rottnest Island17.316.214.413.814.615.214.415.815.313.813.015.818.420.119.316.517.017.618.017.317.318.316.621.219.619.120.019.419.720.119.7
Swanbourne17.416.414.716.216.817.315.817.217.014.512.417.419.821.818.718.919.519.619.217.218.617.519.021.118.620.221.019.920.020.320.2

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
Bickley6.77.94.93.94.35.64.86.35.86.27.47.96.97.810.68.95.85.28.58.98.08.68.69.310.711.08.710.710.011.112.3
Champion Lakes9.010.26.73.85.55.26.58.08.35.610.510.810.49.112.111.28.59.010.711.09.58.89.111.313.913.19.813.714.013.414.7
Garden Island HSF13.112.49.37.47.59.78.510.39.98.710.310.711.110.313.811.58.99.411.312.212.511.611.713.615.315.812.613.513.314.814.7
Gosnells City5.66.78.74.810.610.58.513.210.78.710.510.78.67.512.010.912.68.211.013.612.714.2
Jandakot Aero8.310.24.6-0.40.60.21.83.95.41.810.210.47.64.011.78.55.18.25.310.17.47.96.98.512.010.45.713.414.313.915.1
Medina Research Centre11.111.46.21.32.47.55.05.57.74.510.010.39.37.913.610.16.47.15.511.811.49.98.511.513.212.99.212.513.0
Pearce RAAF7.89.16.80.74.22.24.16.68.25.310.310.69.58.412.48.89.48.110.810.48.79.07.612.113.711.37.913.214.1
Perth Airport8.19.15.70.21.81.52.74.48.22.810.110.69.78.211.39.58.09.110.510.78.77.68.211.413.211.38.014.213.812.913.7
Perth Metro9.39.96.61.31.82.63.44.96.33.410.29.88.96.211.510.47.37.49.110.38.38.07.810.712.411.49.013.814.213.115.4
Rottnest Island11.512.19.29.99.711.69.611.39.710.810.311.012.213.615.612.312.011.712.112.612.212.613.714.216.314.615.011.813.214.815.1
Swanbourne11.111.87.54.75.26.35.96.87.56.09.810.19.69.212.810.78.17.09.611.110.09.39.911.514.014.810.413.414.114.315.1

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) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Bickley 36.4 10.8 5.0 0.2 - 0.2 - - - - 15.6 4.8 0.2 0.2 5.6 16.8 - - - 2.8 6.4 12.0 13.8 0.2 0.2 4.0 - 41.4 28.0 28.0 37.4
Champion Lakes 19.8 6.4 8.2 - - - - - - - 6.6 1.6 - - 0.4 15.2 - - - 3.6 5.4 2.8 9.6 - - - - 22.4 14.6 19.4 7.6
Garden Island HSF 23.0 6.2 17.6 - 0.2 - - - - - 2.8 3.0 0.2 0.2 1.4 12.0 - - - 4.4 26.0 6.0 12.0 0.2 - 9.8 0.2 10.8 10.0 6.6 23.0
Gosnells City 18.4 9.0 7.4 0.2 - - - - »» »» »» 7.8 0.2 - 0.8 15.0 - - »» 2.8 4.4 »» 12.4 0.1 0.2 1.6 - 17.2 7.5 9.6 22.4
Jandakot Aero 27.2 10.0 8.6 - 0.2 - - - - - 7.4 3.2 - - 0.6 9.4 - - - 5.2 6.8 3.2 11.4 - 0.2 1.8 - 30.4 11.2 26.0 18.2
Jarrahdale 39.0 5.2 3.6 - 0.2 0.2 0.2 - 0.2 - 9.6 2.4 0.2 0.2 4.2 25.8 0.4 - 0.2 2.4 17.4 4.0 6.0 2.2 0.2 6.8 0.2 14.0 »» »» 77.4
Medina Research Centre 18.8 9.3 7.9 - - - - - - - 4.2 3.8 - - 2.4 9.0 - - - 5.0 20.4 8.4 6.6 0.3 0.1 3.0 - 17.0 15.4

Mundaring 32.0 20.8 3.4 0.4 0.2 0.2 0.2


11.6 4.0 0.4 0.2 3.2 30.2 0.2 0.2 0.4 4.6 6.8 12.0 12.4 0.8 0.4 6.0 0.2 18.0 34.0 31.6 13.8
Pearce RAAF 13.6 11.6 5.6 - - - - - - - 6.0 6.4 - »» 2.2 18.6 - - - 0.6 8.2 3.2 20.2 - - 1.2 -

17.0 6.0
Perth Airport 21.4 13.6 3.6 - - - - - - - 7.2 3.4 - - 4.0 10.8 - - - 0.8 4.6 5.6 9.4 - 0.4 1.4 - 21.6 12.6 15.0 24.8
Perth Metro 26.8 9.8 5.4 0.2 - - - - - - 6.0 4.8 - - 4.8 13.4 - - - 0.2 4.2 10.6 12.4 - 0.2 1.2 - 14.6 12.4 8.8 25.2
Roleystone 25.8 10.0




0.2

9.6 2.0 0.2
1.0 18.0


2.2 5.0 4.0 13.4 0.4 0.2 3.4
40.6 20.8 22.2 38.8
Rottnest Island 22.0 5.8 10.6 3.6 - - - - - - 1.8 3.8 - - 4.4 4.6 - - - 2.8 66.8 5.6 5.4 1.8 - 3.8 0.2 22.2 3.4 3.8 9.2
Serpentine 35.4 5.0 3.2 - - - - - - - 6.6 4.8 - - 1.4 10.0 0.2 - - 2.6 13.6 4.8 6.0 0.2 - 5.8 - 14.0 12.8 20.0 31.6
Swanbourne 26.8 4.4 6.0 0.2 0.2 - 0.2 - - - 3.4 5.2 - 0.2 0.2 13.6 - - - 15.4 5.6 10.2 13.2 - 0.2 1.6 - 15.6 8.6 8.6 15.8

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 Monday 1 August 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