Perth's driest July for Twenty years(updated)

Rainfall below average: The city received 112.6 millimetres of rainfall over 13 days, compared with the average of 172 mm over 18 days which is the driest July since the 88.0 mm in 1984. Last July Perth registered 146.0 millimetres of rain over 19 days. The greatest daily rainfall this month occurred on the 7th and 8th with 21.0 mm. The last time rainfall exceeded the July mean was in 2001 with 182.6 mm. Historically, July rainfall has ranged from 61.5 mm in 1876 to 425.1 mm in 1958. Total rainfall for January to July this year was 353.0 mm, making it the fifth driest January to July period since the 307.4mm in 1977. The driest January to July period on record was 304.5 mm in 1940, whilst the average rainfall for this period is 557 mm.

Mean daily maximum temperature near average: Perth's mean daily maximum temperature in July was 18.0 degrees Celsius, compared with the average of 18.2 degrees. The lowest daily maximum was a cold 15.0 degrees on the 2nd whilst the highest was a mild 20.7 degrees on the 6th

Mean daily minimum temperature below average: Perth's mean daily minimum temperature in July was 6.8 degrees, compared with the average of 8.3 degrees. This was the lowest mean minimum temperature since the 6.0 degrees in 2001. The daily minima ranged from a cold 0.4 degrees on the 26th, which is the lowest minimum temperature since the 0.1 degrees on 29 July 1998, to a mild 13.9 degrees on the 7th. Perth recorded eleven nights when the minimum temperature was 5 degrees or less, the greatest number of such nights for July since the record in 2001 and 1998 with sixteen; the average is seven.

Mean daily sunshine hours above average: Perth's mean daily sunshine hours in July was 7.1 hours which was above the average of 5.9 hours.

July monthly mean temperature and sunshine
Element	2004	Long-term Average†	Highest	Year	Lowest	Year	Records Commence
Maximum Temperature (°C)	18.0	18.2	19.9	1976/77	15.7	1910	1897
Minimum Temperature (°C)	6.8	8.3	11.4	1921	5.3	1997	1897
Sunshine (hours per day)	7.1	5.9	7.5	1918	3.2	1926	1898
July monthly rainfall and rain days
Element	2004	Long-term Average†	Highest	Year	Lowest	Year	Records Commence
Rainfall (mm)	112.6	172	425.1	1958	61.5	1876	1876
Rain days	13	18	29	1946	6	1918	1876

Climate of Perth in August

August heralds the end of winter and generally shows signs of the forthcoming change in the season. Mean temperatures are generally similar to those in July, but there is a slight reduction in the mean rainfall. Perth can still expect, on average, seven cold nights when the minimum temperature drops to 5 degrees or less. The record number of cold nights in August is 11 in 1999 and 2001. Mean sunshine hours increase, with an extra 1.3 hours a day on average.

August monthly mean temperatures and sunshine
Element	Average	Highest	Year	Lowest	Year	Records Commence
Maximum temperature (°C)	18.6	20.3	1902	16.3	1932	1897
Minimum temperature (°C)	8.1	11.5	1977/83	6.9	1956/2001	1897
Sunshine (hours per day)	7.2	8.4	1902	4.2	1945	1898
August monthly rainfall and rain days
Element	Average	Highest	Year	Lowest	Year	Records Commence
Rainfall (mm)	135	318.1	1945	11.8	1902	1876
Rain days	16	29	1955	4	1902/78	1876

August daily extremes
Element	Highest	Date	Lowest	Date	Records Commence
Maximum temperature (°C)	27.8	21/08/1940	9.9	05/08/1951	1897
Minimum temperature (°C)	16.6	13/08/1976	1.2	21/08/2001	1897
Rainfall 24 hours to 9am (mm)	73.9	14/08/1945	n/a	n/a	1880

Warm days in August: On average, Perth can expect one day when the maximum temperature is 25 degrees or higher. The greatest number of warm days in August was 4 in 1914. There were none in August last year.

Cold days in August: On average, Perth can expect one day when the maximum temperature is 15 degrees or less. The greatest number of such days was 10 in 1917. There was one such day in August last year.

Very cold nights in August: On Average, Perth can expect seven nights when the minimum temperature is 5 degrees or less. The greatest number of such nights was 11 in 1999 and 2001 and there were ten in August last year.

†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.