Thursday 2 December 2004

SEASONAL CLIMATE SUMMARY - WESTERN AUSTRALIAN REGIONAL OFFICE

Drier and cooler spring for Perth(updated)

Rainfall: Spring rainfall in Perth this year was below average. From September to November, Perth received 105.8 millimetres over 33 days compared with the average of 156.0mm over 29 days. It was the driest spring since the 78.4mm in 2000. Last spring, Perth recorded 168.2mm over 31 days. Rainfall totals for individual spring months were: September 35.2mm (average 81mm), October 37.8mm (average 53mm) and November 32.8mm (average 22mm). The wettest day was 10 November when 12.0mm of rain fell.

Mean daily maximum temperatures: The mean daily maximum temperature for Perth this spring of 22.8 degrees Celsius was close to the average of 23.1 degrees. Daily values ranged from a cold 14.5 degrees on 6 September to a hot 36.8 degrees on 22 November. Last spring the mean daily maximum temperature was 23.2 degrees.

Mean daily minimum temperatures: The mean daily minimum temperature for Perth this spring of 11.4 degrees was close to the average of 11.7 degrees. Daily minima ranged from a cold 1.7 degrees on 11 September to a warm 24.4 degrees on 23 November. Perth recorded nine cold nights this spring when the temperature was 5 degrees or less,which was greatest number of cold nights on record for the current Mt Lawley site.The previous record was seven nights in 1994. Last spring the mean minimum temperature was 11.8 degrees.

Mean daily sunshine hours: Perth's mean daily sunshine hours this spring was 9.4 hours,which is near the long term average of 9.3 hours.

Spring mean temperature and sunshine
Element Spring
2004		 Long term Average

Highest

 Year

Lowest

 Year Records Commence
Maximum
Temperature (°C)		 22.8 23.1 24.1 1969 20.0 1971 1897
Minimum Temperature (°C) 11.4 11.7 13.8 1982 10.4 1952 1897
Sunshine
(hours per day)
 9.4 9.3 9.8 1978/2002 6.6 1965 1898
Spring rainfall and rain days
Element Spring
2004 		Long term Average Highest Year Lowest Year Records Commence
Rainfall (mm) 105.8 156 364.0 1890 34.5 1877 1876
Rain days 33 29 48 1898/1926 12 1969 1876

Spring daily extremes
Element Spring
2004		 Date Extreme Date

Records Commence
Highest daily maximum (°C) 36.8 22/11/2004 40.3 * Twice 1897
Lowest daily maximum (°C) 14.5 06/09/2004 11.4 17/09/1917 1897
Highest daily minimum (°C) 24.4 23/11/2004 25.1 24/11/1920 1897
Lowest daily minimum (°C) 1.7 11/09/2004 1.8 23/09/1998 1897
Wettest 24 hours to 9am (mm) 12.0 10/11/2004 68.2 18/10/1995 1876

* Denotes the highest daily maximum temperature recorded on 11 November 2003 and 24 November 1913.

Past Spring in Perth 1994-2004
Season Mean Maximum(°C) Mean Minimum(°C) Total Rainfall (mm) Rain Days Mean Sunshine (hour)
1994 23.8 11.8 101.6 19 9.7
1995 22.8 11.8 208.0 36 9.2
1996 22.8 12.0 222.2 36 9.1
1997 23.1 11.5 158.6 26 9.0
1998 22.6 11.5 161.8 35 9.4
1999 23.0 11.4 206.6 20 9.7
2000 23.7 11.8 78.4 29 9.7
2001 23.0 11.3 173.4 32 9.0
2002 22.9 11.4 153.6 24 9.8
2003 23.2 11.8 168.2 31 9.6
2004 22.8 11.3 105.8 33 9.3

Note: 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 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.

Further information:
John Relf (JR), or John Cramb tel: (08) 9263 2222 or, after hours, the senior forecaster.