Perth in autumn 2012: A warm dry autumn

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

Rainfall

Rainfall across the Perth metropolitan area during autumn 2012 was below average for most sites, apart from Medina, Swanbourne, and Garden Island, which saw near average rainfall. Autumn rainfall totals were generally in the 80 mm to 140 mm range; while Pearce RAAF received the lowest autumn rainfall in the Perth area with 72.4 mm. The dry autumn was primarily due to a very dry March, where most sites reported less than 1 mm for the month, and well below average rainfall in May.

Significant rainfall events during autumn 2012 in Perth:

  • A low pressure system brought moderate to heavy rainfall to the Perth area on 28 and 29 April, with totals mostly in the 20 mm to 30 mm range and isolated falls of up to 60 mm. The daily rainfall total at Swanbourne of 56.2 mm in the 24 hours to 9am on the 29th was the highest daily total of the season in the Perth area, and the second wettest April day for the site.
  • A low and trough brought moderate rainfall in the Perth area between 3 and 6 May, with totals in the 20 to 40 mm range.

Perth Metro recorded 118.4 mm of rainfall on 17 rain days during autumn 2012, which was well below the average of 181.6 mm. Rainfall totals at Perth Metro for individual months this autumn were: March 0.2 mm (average 19.4 mm), April 69.2 mm (average 43.9 mm), May 49.0 mm (average 117.3 mm).

Maximum temperature

Mean daily maximum temperatures for autumn 2012 were generally above average; though some sites in the south and in the hills saw near average daily temperatures. Mean daily maxima for the season were in the mid-to-high twenties.

Autumn 2012 began with heatwave conditions (3 or more consecutive days of daily maximum temperature of 35 °C or higher) in the first half of March, and the daily maximum temperature of 41.9 °C at Gosnells City on 11 March was the highest temperature in the Perth area during autumn. The coldest day for autumn 2012 occurred on 9 May with maxima generally below twenty across the Perth metropolitan area as Bickley recorded a maximum of 16.5 °C.

Perth Metro's mean daily maximum temperature for autumn 2012 was 27.0 °C, 1.1°C above average and the equal third warmest autumn on record with 2009. Last autumn, Perth Metro observed its hottest autumn on record with a mean daily maximum temperature of 27.5 °C. The lowest daily maximum at Perth Metro during autumn 2012 was a mild 19.6 °C, the only sub-20 °C day for the season. Thus Perth Metro observed its lowest number of sub-20 °C days in autumn since records began in 1897, passing the previous record of two sub-20 °C days in 2011. The highest daily maximum during autumn at Perth Metro was a very hot 41.1 °C on 11 March, the hottest March day since the record for March at Perth Metro was set at 42.4 °C on 7 March 2007.

Minimum temperature

Mean daily minimum temperatures during autumn 2012 were near average across the Perth region, with mean daily minima in the low-to-mid teens.

Cold nights were experienced during the latter part of May due to a strong high in the Bight, with Jandakot and Gosnells City observing their coldest autumn night on record on the 25th. The daily minimum temperature of -0.6 °C at Jandakot Aerodrome on the 25 May broke the Jandakot record of -0.1 °C set on 15 May 2010 and was also the lowest temperature in the Perth area for the season. Perth Metro observed a minimum temperature of 1.3 °C on the 25th, which is the lowest autumn minimum temperature observed at the Mt Lawley site since records commenced in 1994, breaking the record of 2.4 °C on 27 May 2004, and 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 for autumn 2012 was 13.6 °C, equal with the average. Daily minima across autumn ranged from a very cold 1.3 °C on 25 May to a warm 20.9 °C on 4 April.

Wind and Sunshine

Perth’s mean daily autumn sunshine was 8.7 hours in 2012, which was the equal fourth sunniest autumn on record with 1994 (sunshine records commenced in 1898). The sunniest autumn on record in Perth was last year (2011) with 9.2 hours of sunshine per day, whilst the average is 8.3.

Further information

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Extremes in autumn 2012
Hottest day 41.9 °C at Gosnells City on 11 Mar
Warmest days on average 27.5 °C at Pearce RAAF
Coolest days on average 24.0 °C at Bickley
Coldest day 16.5 °C at Bickley on 9 May
Coldest night -0.6 °C at Jandakot Aero on 25 May
Coolest nights on average 12.2 °C at Jandakot Aero
Warmest nights on average 17.6 °C at Rottnest Island
15.2 °C at Champion Lakes
Warmest night 23.8 °C at Rottnest Island on 6 Mar
23.4 °C at Pearce RAAF on 28 Apr
Wettest overall 180.4 mm at Jarrahdale
Driest overall 72.4 mm at Pearce RAAF
Wettest day 56.2 mm at Swanbourne on 29 Apr
Highest wind gust 91 km/h at Rottnest Island on 7 May

Record lowest autumn temperature
Lowest temperature
in autumn 2012 (°C)
Previous coolest
for autumn
Years of
record
Average for
autumn
Jandakot Aero -0.6 on 25 May -0.1 on 15 May 2010 22 12.3
Gosnells City 2.5 on 25 May 4.0 on 15 May 2010 20 14.5
Perth Metro* 1.3 on 25 May =1.3 on 11 May 1914 115 13.6



Summary statistics for autumn 2012
Maximum temperatures
for autumn
(°C)
Minimum temperatures
for autumn
(°C)
Rainfall
for autumn
(millimetres)
Mean for
autumn
2012
Diff
from
average
Highest for
autumn
2012
Mean for
autumn
2012
Diff
from
average
Lowest for
autumn
2012
Total for
autumn
2012
Average
for
autumn
Rank of
autumn
2012
Fraction of
autumn
average
Bickley 24.0 +0.3 38.1 12 Mar 12.7 +0.3 5.2 25 May 140.2 207.7 low 68%
Champion Lakes 26.0   39.6 11 Mar 15.2   6.5 25 May 112.8
Garden Island HSF 24.8 +0.6 37.7 11 Mar 16.0 0.0 8.6 25 May 113.0 129.6 average 87%
Gosnells City               25 May 92.7 164.4 low 56%
Jandakot Aero 26.6 +0.8 40.2 11 Mar 12.2 -0.1 -0.6 25 May 123.2 164.7 low 75%
Medina Research Centre 26.7 +1.0 41.1 11 Mar 13.6 +0.4 2.7 25 May 149.0 159.3 average 94%
Pearce RAAF 27.5 +1.2 41.8 12 Mar 13.5 +0.1 1.6 24 May 72.4 133.7 low 54%
Perth Airport 27.0 +1.3 40.9 11 Mar 13.3 +0.2 3.7 26 May 89.8 156.1 low 58%
Perth Metro* 27.0 +1.1 41.1 11 Mar 13.6 0.0 1.3 25 May 118.4 181.6 low 65%
Rottnest Island 24.8 +1.2 37.5 11 Mar 17.6 +0.5 12.4 24 May 81.6 151.7 low 54%
Swanbourne 26.6 +1.1 39.4 11 Mar 15.1 +0.1 6.6 25 May 141.8 147.2 average 96%

Notes

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

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 10 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