Perth in May 2011: A dry start with a wet finish

  • Rainfall: Below average to near average.
  • Maximum temperature: Above average for most sites.
  • Minimum temperature: Near average.

Rainfall

Rainfall in May 2011 across the Perth metropolitan area varied from below average near the base of the Darling Escarpment to near average in coastal and hills suburbs, with monthly rainfall totals generally in the 60 to 100 mm range. Most of the rainfall in the Perth area during May 2011 was registered in the second half of the month, as a couple of strong cold fronts produced moderate to heavy falls on the 20th and 21st, then again overnight on the 30th. Medina Research Station in the south registered 46.4 mm on the 30th, which was the highest daily rainfall recorded in the Perth metropolitan area during May.

The cold front on the 20th brought moderate to heavy rainfall through the Perth area during the morning, with Perth Metro observing 20.4 mm in 41 minutes (between 0811 WST and 0852 WST), which equates to a 1 in 2 to 5 year event. Rainfall totals and rates around Perth were similar, with Champion Lakes observing the highest 24 hour total to 9am with 30.2 mm. Localised minor flooding was reported in the Perth Metropolitan area, primarily due to blocked drainage systems.

Despite recording no rainfall for the first 15 days of the month, Perth Metro recorded 85.0 mm of rainfall on 7 days during May 2011, which is near average. However, the total rainfall for the five months from January to May 2011 at Perth Metro was below average, with 135.0 mm recorded on 21 rain days. The long-term average for this period is 203.3 mm on about 27 days, while the total for the same period last year was 154.2 mm on 16 days.

Maximum temperature

Daytime temperatures during May 2011 were above average for most sites, with mean daily maximum temperatures in the low 20s and generally between 1 °C and 2 °C above normal. The warmest day of the month was the 8th, with several sites registering a daily maximum temperature of 30 °C or above, and Gosnells City's 30.6 °C being the highest daily maxima in the Perth metropolitan area for May 2011.

Perth Metro's mean maximum temperature in May 2011 was 23.2 °C, which is near the average of 22.4 °C. Daily maxima ranged from 17.7 °C on the 21st, to 30.0 °C on the 8th, which was the latest occurrence of 30.0 °C or above in May for 13 years.

Minimum temperature

Overnight temperatures during May 2011 were near average across Perth, with most sites observing mean daily minimum temperatures in the low teens. The coldest night of the month was on the 21st, with several sites registering daily minima temperature 5 °C or lower, and Jandakot Aerodrome recording the lowest minimum in Perth in May with 1.6 °C.

Perth Metro's mean minimum temperature in May was 11.0 °C, which is near the average of 10.6 °C.

Wind and sunshine

A cold front crossed the Perth region during the morning of the 20th with reports of roof and power line damage in Canning Vale at around 0800 WST. Severe wind gusts were observed at Rottnest Island from 1200 to 1300 WST, and a maximum wind gust of 96 km/h was observed at 1235 WST, which was the highest wind gust observed in the Perth region during May 2011.

Perth recorded an average daily sunshine of 7.2 hours in May, above the average of 6.8 hours per day.

Further information

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Extremes in May 2011
Hottest day 30.6 °C at Gosnells City on the 8th
Warmest days on average 24.0 °C at Gosnells City
Coolest days on average 20.6 °C at Bickley
Coldest day 15.3 °C at Bickley on the 21st
Coldest night 1.6 °C at Jandakot Aero on the 21st
Coolest nights on average 9.7 °C at Jandakot Aero
Warmest nights on average 15.7 °C at Rottnest Island
Warmest night 18.9 °C at Rottnest Island on the 9th
Wettest overall 104.0 mm at Bickley
Wettest day 46.4 mm at Medina Research Centre on the 30th
Highest wind gust 96 km/h at Rottnest Island on the 20th

Summary statistics for May 2011
Maximum temperatures
for May
(°C)
Minimum temperatures
for May
(°C)
Rainfall
for May
(millimetres)
Mean for
May
2011
Diff
from
average
Highest for
May
2011
Mean for
May
2011
Diff
from
average
Lowest for
May
2011
Total for
May
2011
Average
for
May
Rank of
May
2011
Fraction of
May
average
Bickley 20.5 +1.2 26.6 8th 10.4 +0.2 6.0 21st 104.0 130.2 average 80%
Champion Lakes 22.7   28.4 8th 12.9   6.0 21st 67.0
Garden Island HSF 22.6   28.4 8th 14.3   11.0 21st 79.0 73.2 average 108%
Gosnells City 23.9 +1.2 30.6 8th         60.6 104.5 low 58%
Jandakot Aero 23.5 +1.5 29.5 8th 9.7 +0.3 1.6 21st 85.6 107.7 average 79%
Medina Research Centre 23.7 +1.7 30.5 8th 11.1 +0.6 4.0 21st 85.0 95.9 average 89%
Pearce RAAF 23.4 +1.5 29.8 8th 11.3 +0.5 3.4 21st 41.8 85.5 low 46%
Perth Airport 23.6 +2.0 29.9 8th 11.0 +0.6 3.1 21st 56.6 100.1 low 57%
Perth Metro 23.2 +0.8 30.0 8th 11.0 +0.5 4.5 21st 85.0 117.4 average 72%
Rottnest Island 21.9 +0.8 27.4 8th 15.7 +0.4 11.8 21st 86.2 106.2 average 81%
Swanbourne 23.5 +1.4 29.6 8th 12.6 0.0 7.3 21st 94.6 89.5 average 106%

Daily maximum temperature
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 22.2 22.7 23.3 24.0 22.8 20.2 22.0 26.6 24.5 22.2 20.4 20.4 20.3 19.8 19.9 21.4 20.0 18.9 21.4 16.2 15.3 17.7 18.8 17.0 17.9 18.0 19.9 22.3 22.4 18.1 17.6
Champion Lakes 23.7 24.8 25.6 26.3 24.3 22.9 24.9 28.4 25.5 24.4 22.8 22.6 22.3 21.6 22.4 23.8 22.2 20.5 23.9 18.0 17.4 19.5 21.7 19.6 19.6 20.4 22.2 25.3 24.0 20.9 20.9
Garden Island HSF 22.6 21.7 25.3 24.8 24.6 20.8 25.8 28.4 21.5 24.9 23.7 23.4 23.6 22.0 23.3 24.2 21.6 21.7 23.7 20.2 17.5 19.1 19.4 21.5 21.8 22.3 21.2 22.2 23.7 21.5 21.8
Gosnells City 25.0 26.1 26.6 27.5 26.0 23.7 26.1 30.6 26.5 25.8 24.0 24.2 24.0 23.0 23.4 25.7 23.3 22.2 25.5 18.5 18.0 21.2 22.2 20.3 21.2 21.5 24.0 26.0 25.8 22.6 21.7
Jandakot Aero 24.6 25.1 26.3 26.2 25.8 23.1 25.8 29.5 25.9 25.2 23.6 23.5 23.4 22.4 23.5 25.0 23.3 21.2 24.8 18.3 17.9 20.6 22.1 20.6 21.0 21.3 23.2 24.8 25.0 22.3 22.6
Medina Research Centre 23.7 25.0 27.6 27.0 26.2 23.6 26.4 30.5 25.5 24.0 23.6 23.9 22.1 23.2 25.9 22.8 22.5 25.6 18.5 18.0 21.0 22.0 21.9 21.0 21.9 24.0 24.8 24.6 21.7 23.1
Pearce RAAF 24.7 25.6 26.1 26.4 26.0 23.4 25.2 29.8 26.8 25.4 23.8 23.5 23.3 21.9 21.0 24.2 22.9 21.5 24.9 18.1 18.1 21.2 21.5 19.6 20.2 20.3 22.4 26.0 25.8 21.3
Perth Airport 24.6 26.0 26.7 26.9 25.7 23.4 25.7 29.9 26.7 25.6 23.7 23.6 23.3 22.9 22.3 24.8 23.1 21.7 25.4 18.2 18.2 21.9 22.0 19.9 20.8 21.1 23.1 25.3 25.6 21.9 21.2
Perth Metro 24.2 25.3 26.5 26.5 25.0 23.0 25.2 30.0 25.3 25.3 23.5 23.3 23.0 22.6 21.8 24.0 22.4 20.9 24.8 18.5 17.7 20.6 21.2 20.5 20.5 21.5 22.8 24.8 24.6 21.7 21.2
Rottnest Island 21.9 22.5 25.2 24.5 24.1 20.0 24.0 27.4 21.7 23.5 21.9 21.2 22.0 21.1 21.9 23.0 21.6 20.9 23.4 19.5 16.9 18.8 19.0 21.4 19.6 20.3 20.8 22.6 23.0 21.9 22.0
Swanbourne 25.0 25.8 26.5 25.3 25.1 23.8 26.0 29.6 24.8 26.2 24.4 24.3 23.9 22.9 22.3 24.5 23.2 22.4 24.5 19.4 18.4 20.0 21.3 21.8 21.3 22.0 23.4 23.4 23.8 22.2 22.5
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) 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 10.5 10.4 10.5 11.4 11.6 10.4 8.5 11.7 14.0 11.5 10.4 7.7 8.6 9.3 12.0 13.1 14.1 11.1 8.9 12.8 6.0 8.9 8.8 9.7 9.6 9.6 7.9 8.5 10.1 13.4 11.8
Champion Lakes 12.5 14.1 14.2 14.1 12.0 12.8 12.7 15.8 13.7 15.2 14.5 11.9 12.9 13.5 16.4 16.8 14.5 11.6 10.9 16.8 6.0 7.7 9.5 10.7 13.2 12.3 12.0 11.5 11.5 15.4 14.2
Garden Island HSF 13.8 14.7 15.0 14.7 13.0 14.1 13.5 17.0 16.7 15.4 14.3 12.9 13.8 14.5 17.1 16.8 15.7 14.3 14.1 17.1 11.0 11.2 13.3 11.6 14.5 13.1 13.3 11.6 12.9 15.9 16.5
Gosnells City 10.0 10.2 17.9 11.6 9.2 12.8 12.4 15.4 12.0 12.6 11.0 12.1 10.2 17.2   6.0 7.8 9.8 12.2 12.4 9.0 9.0 9.0 13.9
Jandakot Aero 6.7 9.2 12.1 7.7 6.3 8.6 11.2 15.7 11.3 14.7 13.4 9.3 12.2 12.7 16.1 11.9 11.7 7.8 5.2 15.1 1.6 2.6 4.2 6.9 7.7 10.0 11.8 5.0 5.0 15.3 12.3
Medina Research Centre 8.2 11.8 12.0 10.8 8.4 10.4 12.5 16.0 14.0 13.6 8.4 12.5 12.1 16.7 14.0 12.7 11.1 9.9 15.4 4.0 5.4 6.4 7.4 11.5 11.6 11.2 8.7 6.5 15.2 15.1
Pearce RAAF 7.0 10.0 9.9 10.1 7.0 12.7 14.0 16.5 9.9 15.9 13.4 10.5 11.3 11.6 15.8 15.6 14.9 8.3 13.2 17.3 3.4 3.8 6.2 7.5 13.1 14.0 13.3 8.6 7.5 15.5
Perth Airport 7.4 10.3 10.5 10.2 9.8 14.1 11.5 15.2 9.7 15.2 14.0 9.1 11.4 12.7 14.8 15.7 12.4 8.8 10.5 15.6 3.1 4.1 4.4 6.8 12.2 11.5 12.0 10.8 8.0 15.3 12.6
Perth Metro 8.3 10.5 11.3 9.8 8.9 12.3 12.4 15.5 12.9 15.3 13.4 10.9 12.2 12.8 15.0 14.0 14.5 9.7 7.5 15.6 4.5 4.9 5.4 6.9 10.3 12.2 11.6 7.2 6.7 15.2 12.0
Rottnest Island 15.6 15.7 16.5 17.4 17.7 15.2 14.4 16.5 18.9 16.1 14.8 15.0 15.2 15.5 16.1 17.4 17.9 15.3 16.3 16.9 11.8 13.9 14.0 13.3 15.1 15.2 14.3 15.2 16.4 16.5 16.2
Swanbourne 10.7 12.9 13.0 13.1 12.8 11.6 12.7 15.5 14.7 15.0 13.3 12.0 12.6 13.3 15.4 14.8 15.3 12.1 10.7 16.4 7.3 8.2 10.0 9.7 11.9 12.0 12.2 10.8 9.2 15.1 16.7

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 - - - - - - - - - - - - - - 0.2 - - 4.4 0.2 27.8 25.4 - - - - - - - - 28.2 17.8
Champion Lakes - - - - - - - - - - - - - - - 0.8 0.2 4.8 0.2 30.2 10.6 - - - - - - - - 17.8 2.4
Garden Island HSF - - - - - - - - - - - - - - - - 3.4 11.4 - 10.8 9.8 - - - - - - - - 37.4 6.2
Gosnells City - - - - - - - - - - - - - »» »» 1.2 0.4 5.8 0.1 19.0 8.7 1.0 1.0 - - - - - - 18.0 5.4
Jandakot Aero - - - - - 0.6 0.2 - - - - - - - - 1.0 - 6.6 - 29.4 9.6 - - - - - - - - 35.0 3.2
Jarrahdale - 0.4 0.2 0.2 - 0.2 0.2 - - - - - - - - - 0.2 3.2 0.2 23.2 18.8 0.4 0.2 - - - - 0.2 0.2 24.4 4.0
Medina Research Centre - - - - - - - - - - - - - - - 0.4 0.8 8.8 - 11.6 11.2 - - - - - - - - 46.4 5.8
Mundaring 0.2 0.2


0.2



0.2


0.4 1.4 0.8 5.0 0.2 4.0 23.2 0.2 0.2 0.2




23.0 5.4
Pearce RAAF - - - - - 0.8 -
- - - - - - - - 0.4 5.2 - 1.2 10.6 - - - - - - - - 21.4 2.2
Perth Airport - - - - - - - - - - - - - - - 0.2 0.4 4.8 - 16.4 11.6 - - - - - - - - 18.2 5.0
Perth Metro - - - - - - - - - - - - - - - 0.8 1.6 8.2 - 24.2 14.6 - - - - - - - - 25.0 10.6
Rottnest Island - - - - - - - - - - - - - - - 0.2 2.4 12.0 - 15.8 9.2 - - - - - - - - 45.4 1.2
Serpentine - - - - - - - - - - - - - - - 0.2 - 4.8 - 15.2 12.8 - - - - - - - - 34.6 8.8
Swanbourne - - - - - - - - - - - - - - - 0.6 8.4 11.2 - 28.2 13.4 - 0.2 - - - - - - 28.0 4.6

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 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

This statement was prepared before all data for the period were available. This may affect some of the statistics presented.

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 1 pm on Wednesday 1 June 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