Perth in May 2012: A dry month

This statement was prepared before all data for the period were available. This may affect some of the statistics presented.
  • Rainfall: Below to very much below average at most sites
  • Maximum temperature: Near average to above average at some sites
  • Minimum temperature: Near average

Rainfall

Rainfall totals in May 2012 were generally below to very much below average in the Perth metropolitan area; however, a few sites recorded close to average rainfall. Pearce RAAF, Mundaring and Perth Airport observed their driest May in over 10 years, with these sites recording less than 40% of their average rainfall for May.

A low and trough moved across the southwest of WA from 3 to 6 May 2012, bringing the first significant rainfall to the Perth area for the month, with a few moderate falls observed over the period. Generally light rainfall continued for the next few days, with a cold front crossing the metropolitan area on the 7th and a westerly flow maintaining showers through to the 10th. Further cold fronts crossed the southwest of the state, bringing light falls to the Perth area from the 13th to 17th, before a strong high moved into the Bight for much of the remainder of the month. A slow moving cold front moved over Perth on the last day of the month bringing some showers to break the two week dry spell.

Perth Metro recorded 49.0 mm of rainfall on 9 rain days in May 2012, well below the long term average of 117.3 mm on 11.3 rain days. Historically, May rainfall extremes have ranged from 14.1 mm in 1964 to 308.1 mm in 1879. Last May (2011), Perth Metro recorded 85.0 mm on 7 rain days. For the year to date (January to May), Perth Metro has recorded 160.8 mm of rainfall on 25 rain days. The average for the five months is 202.8 mm on 26.5 rain days, whilst last year (2011) Perth Metro recorded 135.0 mm on 21 rain days.

Maximum temperature

Mean maximum temperatures in May 2012 were generally close to average across the Perth metropolitan area and in the low twenties; though Pearce RAAF and Perth Airport recorded mean maxima for the month over 1 °C higher than normal.

Warm conditions in the mid-to-high twenties were experienced in the Perth region on 2 and 3 May 2012 in warm northerly winds as a trough approached from the west, with all sites in the region observing their warmest day for the month in this period, and Pearce RAAF recording the highest temperature for the month in the Perth metropolitan area with 28.2 °C. Cooler temperatures followed due to a westerly flow with most sites observing their coolest day on the 9th, including Bickley which observed the coolest day in the Perth area in May with a maximum of 16.5 °C. A return to warm northeast winds on the 11th and 12th saw maxima return to the mid-twenties. Frontal activity to the south saw cooler days from the 14th to 16th, before a high moved into the Bight and brought some warmer days from the 19th to 21st. A weak westerly flow saw cooler days on the 22nd and 23rd, before a strong high again moved into the Bight with temperatures remaining in the low-to-mid twenties for the remainder of the month.

Perth Metro's mean daily maximum temperature in May was 23.1 °C, which is close to the average of 22.4 °C. Daily maxima ranged from a mild 19.6 °C on the 9th to warm 27.3 °C on the 2nd. Despite a near average mean maximum temperature, Perth Metro observed 30 days of 20 °C or greater in May, breaking the record of 29 set in 2011. The lowest maximum temperature for May 2012 of 19.6 C was the highest observed 'lowest maximum temperature' on record for May, breaking the record of 19.3 C set in 1983 (daily temperature records commenced in 1897).

Perth Metro's mean daily maximum temperature for the year to date (January to May) period is 29.1 °C, which is the equal 3rd warmest (equal with 2009) since records commenced in 1897. The warmest year to date (January to May) was 29.8 °C, recorded last year (2011), whilst the long-term average for the five month period is 28.0 °C.

Minimum temperature

Mean minimum temperatures in May 2012 were generally close to average across the Perth metropolitan area.

May 2012 commenced with warmer than normal nights observed for much of the first half of the month, with the warmest night at all sites occurring between the 3rd and 5th, coinciding with the warmest daytime temperatures for the month. In contrast, cooler than normal temperatures were observed for much of the second half of the month, with several strong highs over the south of the state directing cool dry air over the region for much of the period. Very cold conditions were observed at most sites from the 23rd to 27th, with Jandakot and Gosnells City observing their coldest May night on record on the 25th, and Jandakot recording a minimum of -0.6 °C, the lowest temperature recorded in the Perth metropolitan area for May.

Perth Metro observed a minimum temperature of 1.3 °C on the 25th, which is the lowest May minimum temperature observed at the Mt Lawley site since records commenced in 1994, breaking the record of 2.4 °C on 27 May 2004. It was also the equal coldest May night observed at any of the past official Perth Metro sites (commencing in 1897), equal with the 1.3 °C observed on 11 May 1914.

Perth Metro's mean daily minimum temperature in May was 10.4 °C, which is close to the average of 10.7 °C. The warmest night during the month was 18.9C on the 3rd.

Sunshine

Perth recorded an average daily sunshine of 7.5 hours in May, which was the sunniest May since the 8.1 hours in 2009 (the sunniest May on record). The average sunshine hours for May is 6.9 hours per day.

Further information

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Extremes in May 2012
Hottest day 28.2 °C at Pearce RAAF on the 2nd
Warmest days on average 23.7 °C at Gosnells City
Coolest days on average 19.8 °C at Bickley
Coldest day 16.5 °C at Bickley on the 9th
Coldest night -0.6 °C at Jandakot Aero on the 25th
Coolest nights on average 9.0 °C at Jandakot Aero
Warmest nights on average 15.6 °C at Rottnest Island
Warmest night 18.9 °C at Perth Metro on the 3rd
Wettest overall 93.0 mm at Jarrahdale
Wettest day 33.4 mm at Medina Research Centre on the 4th
Highest wind gust 91 km/h at Rottnest Island on the 7th

Lowest total May rainfall for at least 10 years
Total rainfall
for May 2012 (mm)
Most recent May
at least this dry
Years since
drier
Average for
May
Pearce RAAF 23.6 4.2 in 1964 48 84.4
Gosnells City 33.6 17.3 in 1964* 46 102.8
Mundaring 53.6 40.2 in 2000 12 136.4
Perth Airport 36.6 20.8 in 2000 12 99.2

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




Record lowest May temperature
Lowest temperature
in May 2012 (°C)
Previous coolest
for May
Years of
record
Average for
May
Jandakot Aero -0.6 on the 25th -0.1 on the 15th in 2010 22 9.4
Gosnells City 2.5 on the 25th 4.0 on the 15th in 2010 20 11.9
Perth Metro* 1.3 on the 25th 1.3 on the 11th in 1914 115 10.7



Summary statistics for May 2012
Maximum temperatures
for May
(°C)
Minimum temperatures
for May
(°C)
Rainfall
for May
(millimetres)
Mean for
May
2012
Diff
from
average
Highest for
May
2012
Mean for
May
2012
Diff
from
average
Lowest for
May
2012
Total for
May
2012
Average
for
May
Rank of
May
2012
Fraction of
May
average
Bickley 19.8 +0.3 24.1 3rd 10.3 +0.1 5.2 25th 61.4 128.7 low 48%
Champion Lakes 22.2   26.0 2nd 12.7   6.5 25th 44.6
Garden Island HSF 21.7 +0.1 26.5 2nd 13.8 -0.2 8.6 25th 67.2 72.7 average 92%
Gosnells City 23.7 +0.9 27.2 2nd         33.6 102.8 v low 33%
Jandakot Aero 22.7 +0.6 26.5 2nd 9.0 -0.4 -0.6 25th 53.6 106.3 low 50%
Medina Research Centre 23.0 +0.9 27.1 3rd 10.7 +0.2 2.7 25th 92.0 97.5 average 94%
Pearce RAAF 23.2 +1.3 28.2 2nd 10.7 -0.1 1.6 24th 23.6 84.4 v low 28%
Perth Airport 23.1 +1.3 27.1 2nd 10.2 -0.2 3.7 26th 36.6 99.2 low 37%
Perth Metro* 23.1 +0.7 27.3 2nd 10.4 -0.3 1.3 25th 49.0 117.3 low 42%
Rottnest Island 21.8 +0.7 25.8 3rd 15.6 +0.3 12.4 24th 45.2 69.5 average 65%
Swanbourne 23.1 +0.8 27.4 2nd 12.6 0.0 6.6 25th 56.4 87.7 low 64%

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 18.8 23.1 24.1 18.0 20.1 17.3 17.8 17.6 16.5 18.7 20.3 22.8 20.1 17.4 16.6 19.3 18.8 20.8 21.6 23.8 23.3 19.5 17.0 18.7 18.7 21.1 20.8 19.8 20.2 21.8
Champion Lakes 21.5 26.0 25.2 20.7 22.0 19.0 20.9 20.0 19.0 21.0 22.8 25.7 22.5 20.5 20.0 21.1 21.6 22.8 24.5 25.6 24.0 19.7 19.7 22.0 22.1 22.8 23.4 22.7 22.9 24.1
Garden Island HSF 23.0 26.5 25.4 20.0 22.6 19.6 21.2 20.7 20.0 19.9 21.3 25.5 22.0 20.4 19.3 19.5 21.1 22.7 23.2 21.8 20.5 18.7 20.6 20.4 20.7 22.0 23.8 21.9 22.9 23.3
Gosnells City 22.5 27.2 27.0 21.5 23.0 22.0 21.5 20.8 22.2 24.2 27.0 23.5 24.2 21.0 22.3 22.0 24.0 26.0 27.0 26.0 21.5 21.0 23.0 22.0 24.0 25.0 24.0 25.0 26.0
Jandakot Aero 22.1 26.5 26.4 20.8 22.5 20.0 21.9 21.4 19.7 21.4 23.1 26.3 22.4 20.2 20.3 21.4 21.7 23.3 24.9 26.0 24.8 20.5 20.4 21.4 21.1 23.1 24.0 23.1 23.7 25.4
Medina Research Centre 23.0 26.9 27.1 20.2 22.5 19.6 22.2 21.0 21.9 21.5 24.0 26.5 22.7 20.8 20.6 21.5 21.6 24.1 25.1 26.0 24.4 20.1 20.5 22.4 22.1 23.9 24.1 23.5 24.1 25.2
Pearce RAAF 23.0 28.2 27.7 21.0 23.7 21.8 22.6 21.5 21.2 21.2 23.0 26.9 23.4 20.5 20.6 21.6 21.9 22.9 24.7 26.3 25.8 22.0 20.6 22.2 22.4 24.0 24.1 22.4 24.2 25.7
Perth Airport 22.2 27.1 26.4 20.6 22.5 20.5 22.1 21.2 19.1 22.0 23.7 26.6 22.5 21.1 20.5 22.1 21.4 23.6 24.9 26.6 25.8 21.7 20.6 21.9 21.8 23.8 24.2 22.9 24.3 25.6
Perth Metro 22.8 27.3 26.3 20.6 22.5 20.5 21.9 21.8 19.6 21.7 24.0 26.3 22.9 21.8 20.3 21.7 21.4 23.8 25.2 26.5 25.4 21.3 21.1 22.0 21.9 23.5 24.5 23.3 24.4 25.8
Rottnest Island 21.0 25.6 25.8 21.1 22.8 20.1 21.6 21.1 20.8 20.2 20.7 25.2 22.9 21.1 19.9 19.8 21.6 22.3 23.1 22.2 21.2 18.6 19.5 20.8 20.6 22.0 22.5 22.2 23.7 23.8
Swanbourne 23.4 27.4 26.2 20.9 23.0 20.6 21.8 21.5 19.5 21.7 24.3 26.5 23.5 21.8 21.4 21.3 20.5 24.4 25.5 26.5 24.9 20.1 21.2 22.6 22.1 23.6 25.0 23.7 24.7 24.2

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
Bickley10.69.113.916.214.812.811.113.09.912.010.19.613.510.711.59.29.210.08.610.010.69.57.15.45.26.99.310.16.69.712.0
Champion Lakes14.014.018.318.317.715.213.915.512.213.412.313.712.911.310.511.49.412.312.313.612.911.59.08.96.59.711.413.410.613.912.3
Garden Island HSF13.614.918.817.918.217.614.817.013.315.113.715.214.616.214.712.112.513.412.811.113.113.211.39.38.69.610.914.612.413.415.1
Gosnells City16.514.012.211.511.510.514.111.811.014.08.56.010.510.010.010.09.07.55.02.54.04.513.09.212.59.5
Jandakot Aero10.29.918.717.716.914.412.916.710.613.08.011.010.810.77.96.44.98.89.47.48.45.04.32.6-0.60.84.210.14.47.07.0
Medina Research Centre12.512.118.518.117.516.314.316.712.313.59.512.011.214.010.68.47.48.610.58.38.69.35.03.82.72.84.912.55.811.113.7
Pearce RAAF14.215.818.618.417.014.812.314.711.712.010.514.311.89.610.78.24.56.49.213.412.36.87.91.62.0 3.7 5.7 12.65.813.910.3
Perth Airport12.812.517.818.116.313.912.615.611.412.79.313.412.09.89.88.06.88.68.010.28.46.05.34.14.33.75.311.710.38.38.8
Perth Metro12.010.718.918.616.914.813.516.611.913.69.711.511.411.311.38.37.49.48.19.28.67.39.65.61.33.56.210.55.19.49.7
Rottnest Island14.516.318.418.118.316.315.716.114.515.815.116.018.215.716.614.515.115.514.516.215.914.812.612.413.613.915.316.015.316.616.2
Swanbourne13.413.118.618.117.616.814.216.412.814.111.713.914.515.312.610.49.911.110.510.911.09.59.28.46.67.99.812.79.914.614.1

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)12345678910111213141516171819202122232425262728293031
Bickley - - - 2.8 22.0 6.8 5.0 15.4 0.6 1.4 0.2 - - 1.8 2.4 2.8 - 0.2 - - - - - - - - - - - - -
Champion Lakes - - - 13.8 9.2 2.8 2.2 11.8 1.0 1.0 0.2 - - - 2.4 0.2 - - - - - - - - - - - - - - -
Garden Island HSF - - - 25.2 16.0 2.2 0.8 7.8 4.8 5.0 - - - 1.0 1.6 0.8 0.2 - - - - - - - - - - - - - 1.8
Gosnells City - - - 6.0 9.6 4.8 - 8.4 1.3 1.4 - - - 0.1 1.8 0.2 - - - - - - - - - - - - - - -
Jandakot Aero - - - 15.8 13.2 5.6 2.0 13.4 0.6 1.4 - - - 1.0 0.4 0.2 - - - - - - - - - - - - - - -
Jarrahdale 0.2 0.2 - 27.0 21.6 4.6 3.4 27.0 1.8 2.0 0.2 0.2 0.2 1.8 0.2 0.4 0.2 - 0.2 0.2 0.2 0.2 0.2 0.2 0.2 - 0.4 - 0.2 - -
Medina Research Centre - - - 33.4 21.2 2.2 1.0 15.6 7.6 4.4 - - - 3.8 1.4 1.4 - - - - - - - - - - - - - - -
Mundaring


2.8 16.6 3.2 3.6 14.6 0.2 8.0 0.2

1.2 2.2 0.4 0.2



0.2 0.2







Pearce RAAF - - - »» 7.2 2.8 0.8 5.4 0.6 2.2 - - - - 2.6 0.8 0.2 - - - - - - - -

- 0.2 - -
Perth Airport - - - 1.8 11.6 4.0 2.2 6.0 0.2 9.2 - - - 1.0 0.6 - - - - - - - - - - - - - - - -
Perth Metro - - - 6.4 11.2 10.4 3.4 4.6 0.6 11.6 - - - - 0.6 0.2 - - - - - - - - - - - - - - -
Roleystone


7.4 14.0 4.8 4.6 14.6






















Rottnest Island 0.6 - - 11.6 22.8 1.4 0.2 3.6 3.0 0.8 - - - 0.2 0.2 - - - - - - - - - - - - - - - 0.8
Serpentine - - - 32.6 31.8 3.4 2.2 13.8 1.2 2.0 0.2 - - 1.0 0.2 - - - - - - - - - - - - - - - -
Swanbourne - - - 15.8 11.8 2.0 2.4 3.8 2.2 12.4 - - - - 1.8 4.0 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

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 11 am on Thursday 31 May 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