Perth in summer 2010/11: Very hot summer in Perth

  • Rainfall: Above average
  • Maximum temperature: Above average
  • Minimum temperature: Above to very much above average

Rainfall

Rainfall in the Perth metropolitan area during summer 2010/11 was generally above average, with totals for the three months mainly in the 30 to 50 mm range. A tropical low off the west coast that brought flooding rain to the Gascoyne caused moderate rainfall in the Perth region on 20 and 21 December. Moderate rainfall was also reported across the city in the 24 hours to 9am on 6 January 2011 due to a cold front and middle level cloudband, while a line of thunderstorms, originating from the north, crossed the Perth Metropolitan area during the afternoon of 29 January 2011 causing moderate rainfall at several locations. Rainfall during February 2011 in the Perth area was generally below average, with several sites observing no rainfall for the month, however, this is not uncommon for this time of year.

Severe thunderstorms developed during the afternoon of 28 February 2011 and produced heavy rainfall in northern, eastern and southern parts of the Perth Metropolitan area during the afternoon. Rainfall totals in the 24 hours to 9am on 1 March 2011 (which was likely to have fallen in the afternoon of 28 February) observed at Bureau of Meteorology weather stations were 19.2 mm at Champion Lakes, 19.0 mm at Gosnells City, 9.6 mm at Jarrahdale, 4.2 mm at Bickley and 0.4 mm at Serpentine. Hourly data at Champion Lakes and Bickley indicate that Champion Lakes observed 19.2 mm between 1628 and 1800 WST on the 28 February, while Bickley observed 4.2 mm between 1556 and 1800 WST.

Rottnest Island recorded 80.0 mm during summer 2010/11, almost three times the summer average, and the 8th highest summer rainfall total since records commenced in 1879. The highest summer rainfall at Rottnest Island is 180.9 mm in the 1954/55 summer.

Perth Metro received 48.0 mm on 12 rain days over summer 2010/11, above the average of 35.0 mm on 8.2 rain days. Individual monthly totals for summer 2010/11 were: 17.4 mm in December (average 12.8 mm); 30.2 mm in January (wettest since the 139.0 mm in 2000; average 9.5 mm); and 0.4 mm in February (average 12.7 mm). The wettest day at Perth Metro during summer 2010/11 was 13.6 mm observed in the 24 hours to 9am on 6 January 2011. Last summer (2009/10), Perth Metro recorded 0.2 mm on 1 rain days, which was the driest summer since records commenced in 1876.

Maximum temperature

After a cooler than normal start to summer 2010/11, mean daily maximum temperatures were mostly warmer than normal, with most sites 1 to 2 °C above normal and a few sites more than 2 °C above normal. Perth Metro's mean daily maximum temperature in summer 2010/11 was 32.0 °C, which is 1.9 °C above average and equal hottest summer on record with 1977/78 and 2009/10. Swanbourne and Medina Research Centre also broke their hottest summer on record in terms of daytime temperatures.

Heatwave conditions (three or more days of 35.0 °C or more) were evident at many sites around the Perth area from 25 to 27 December 2010, with the hottest day of summer 2010/11 occurring during this period when Pearce RAAF observed 42.1 °C on the 27th. January 2011 also saw heatwaves from the 1st to 4th and from the 27th to 30th January 2011, which helped Perth Metro record its 7th hottest January on record. Consistently warm conditions were experienced throughout much of February 2011, particularly in the latter half of the month when very hot conditions were experienced due to a broad surface trough over much of WA and another trough off the west coast dragging hot and humid northeasterly winds over Perth. Heatwave conditions were observed at most Perth stations during this time, with daily maximum temperatures generally in excess of 35 °C from the 21st through to the 28th, with little to no relief provided by the sea breeze. Perth Metro observed its 3rd highest February mean daily maximum temperaure.

During summer 2010/11, Perth Metro observed a total of 60 days when the maximum temperature had been 30 °C or higher, breaking the previous record of 56 days observed in summer 2009/10. The average for the number of days at 30 °C or higher in summer is 44.5 days at Perth Metro, from observations beginning in 1897. Perth Metro also observed 28 days when the maximum temperature was 35 °C or higher in summer, which is the 3rd highest, behind the record of 31 days in 1977/78 and the 29 days in 1961/62. The average for the number of days 35 °C or higher in summer is 18 days.

Daily maxima during summer 2010/11 at Perth Metro ranged from a mild 21.1 °C on 3 December 2010 to a very hot 40.4 °C on 29 January 2011.

Minimum temperature

Minimum temperatures across Perth during summer 2010/11 were very much above average, with a number of stations breaking their highest summer mean daily minimum records. Most sites were 1 to 2 °C above normal and a few sites more than 2 °C above normal. Apart from the first few weeks of December 2010, overnight summer temperatures across Perth were consistently above average, particularly during the second half of February 2011 where nearly all sites observed minimum temperatures of over 20 °C from the 14th through to the end of the month.

Perth Metro observed 15 consecutive nights with a maximum temperature of 20 °C or more during February 2011 (14th to 28th) which is the longest hot spell of this kind, breaking the record of 13 nights observed in 1985 (17 February to 1 March) and in 1990 (23 February to 7 March).

Perth Metro's mean daily minimum temperature in summer 2010/11 was 19.0 °C, which is the highest since the 19.2 °C in 1991/92. The average for summer is 17.3 °C. Daily minima at Perth Metro during summer 2010/11 ranged from a coo1 9.4 °C on 4 December 2010 to a hot 26.1 °C on 28 January 2011.

Wind and Sunshine

Very strong easterly winds were observed in the Perth area on 26 December 2010, and on 5 and 6 February 2011 which were associated with significant bushfires at Redhill and Roleystone/Kelmscott.

Perth’s average daily sunshine hours during summer 2010/11 was 11.0 hours, close to the average of 11.4 hours.

Other Phenomena

The average dew-point temperature, a measure of the moisture content of the air (the temperature to which air - at constant atmospheric pressure - must be cooled in order for dew to occur) at Perth Metro during summer2010/11 was 13.6 °C, which is 1.0 °C above the average and lead to uncomfortable conditions across Perth for much of summer 2010/11, particularly during January and February.

Severe thunderstorms developed in the afternoon of 28 February in the north, east and south of Perth in a hot, moist and unstable atmosphere. The worst affected suburbs were Ellenbrook, Middle Swan, Midland, Mundaring and Kalamunda, with reports of damage, localised flooding and loss of power.

Further information

Media
(03) 9669 4057
Enquiries

Extremes in summer 2010-11
Hottest day 42.1 °C at Pearce RAAF on 27 Dec 2010
Warmest days on average 33.9 °C at Gosnells City
Coolest days on average 27.7 °C at Rottnest Island
Coldest day 19.3 °C at Bickley on 3 Dec 2010
Coldest night 5.5 °C at Jandakot Aero on 4 Dec 2010
Coolest nights on average 16.2 °C at Bickley
Warmest nights on average 19.7 °C at Rottnest Island
Warmest night 27.5 °C at Medina Research Centre on 28 Jan 2011
Wettest overall 80.0 mm at Rottnest Island
Wettest day 28.2 mm at Bickley on 6 Jan 2011
Highest wind gust 98 km/h at Perth Airport on 26 Dec 2010


Record highest summer mean daily maximum temperature
Mean daily maximum
temperature
for summer 2010-11 (°C)
Previous warmest
for summer
Years of
record
Average for
summer
Medina Research Centre 32.0 31.8 in 2009 21 29.9
Swanbourne 31.4 30.7 in 2009 17 29.1
Perth Metro* 32.0 = 32.0 in 1977 & 2009 16 30.4



Record highest summer mean daily minimum temperature
Mean daily minimum
temperature
for summer 2010-11 (°C)
Previous warmest
for summer
Years of
record
Average for
summer
Perth Airport 18.5 18.4 in 1977 66 16.4
Pearce RAAF 18.6 18.3 in 1977 49 16.3
Medina Research Centre 18.5 17.6 in 2007 21 16.4
Jandakot Aero 17.9 17.4 in 1991 20 15.9
Swanbourne 18.9 18.4 in 1999 17 17.6
Bickley 16.2 15.6 in 2009 16 14.7


Summary statistics for summer 2010-11
Maximum temperatures
for summer
(°C)
Minimum temperatures
for summer
(°C)
Rainfall
for summer
(millimetres)
Mean for
summer
2010-11
Diff
from
average
Highest for
summer
2010-11
Mean for
summer
2010-11
Diff
from
average
Lowest for
summer
2010-11
Total for
summer
2010-11
Average
for
summer
Rank of
summer
2010-11
Fraction of
summer
average
Bickley 30.9 +1.2 38.8 27 Dec 2010 16.2 +1.5 8.4 4 Dec 2010 55.2 49.3 high 112%
Champion Lakes 32.2   39.9 25 Dec 2010 19.4   9.5 4 Dec 2010 43.6
Garden Island HSF 29.1   37.5 21 Feb 2011 19.5   13.5 10 Dec 2010 32.0 26.6 average 120%
Gosnells City 33.9 +1.9 42.0 29 Jan 2011     9.0 4 Dec 2010 40.8 38.2 average 107%
Jandakot Aero 32.6 +2.2 41.0 27 Dec 2010 17.9 +2.0 5.5 4 Dec 2010 42.2 42.6 average 99%
Medina Research Centre 32.0 +2.1 40.5 27 Dec 2010 18.5 +2.1 7.5 4 Dec 2010 31.1 40.8 average 76%
Pearce RAAF 33.8 +1.5 42.1 27 Dec 2010 18.6 +2.2 5.7 4 Dec 2010 27.8 26.3 average 106%
Perth Airport 33.0 +2.2 41.8 29 Jan 2011 18.5 +2.1 5.8 4 Dec 2010 59.6 34.4 high 173%
Perth Metro* 32.0 +1.9 40.4 29 Jan 2011 19.0 +1.7 9.4 4 Dec 2010 48.0 35.0 high 137%
Rottnest Island 27.7 +1.7 35.7 21 Feb 2011 19.7 +1.1 13.8 3 Dec 2010 80.0 28.0 highest 286%
Swanbourne 31.4 +2.3 39.6 28 Feb 2011 18.9 +1.3 10.3 4 Dec 2010 38.6 31.0 high 125%

Notes

A Seasonal 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 3 March 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.
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