Tuesday 1 August, 2006

MONTHLY CLIMATE SUMMARY - WESTERN AUSTRALIA REGIONAL OFFICE

Driest year to date on record for Perth

Seven-monthly rainfall - record low: The total rainfall for January to July this year was 215.6 mm, making it the driest such period on record. The previous record was 304.5 mm in 1940. The average is 555 mm.

Perth's top 10 driest years to date (January to July total)
Season	Rainfall (mm)	Rain Days	Ranking
2006	215.6	46	1
1940	304.5	53	2
1977	307.4	46	3
1894	340.0	53	4
1914	345.5	64	5
2004	353.0	51	6
1979	362.8	62	7
1949	364.4	64	8
1972	365.0	57	9
1993	366.0	51	10

July Rainfall - well below average: The city received 81.0 mm of rainfall over 13 days in July compared with the average of 171 mm over 17 days. This was Perth's sixth driest July on record, the driest being 61.5 mm in 1876. The wettest day in July 2006 was the 25th when 19.4 mm was recorded. Last July Perth registered 62.8 mm on 14 days, the second driest July on record for Perth.

June and July rainfall - record low: The total rainfall for June and July this year was 105.6 mm, making it the driest June and July period for Perth on record. The previous record was 166.2 mm in 1977. The average is 350 mm.

Mean daily maximum temperature - near average: Perth's mean daily maximum temperature in July was 18.8°C, compared with the average of 18.3°C. Daily maxima ranged from a cool 14.6°C on the 21st to a warm 23.0°C on the 8th.

Mean daily minimum temperature - below average: Perth's mean daily minimum temperature in July was 6.5°C, compared with the average of 8.0°C. This was the lowest mean daily minimum temperature for July since the 6.0 degrees in 2001. Daily minima ranged from a very cold 0.2°C on the 22nd to a mild 13.6°C on the 9th.

*Denotes the highest maximum temperature for July on record on the following dates: 17 & 18 July 1976.
**Denotes the lowest minimum temperature for July on record on the following dates: 15 July 1997 and 27 July 1998.

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. Mean sunshine hours increase, with an extra 1.0 hours per day on average.

Warm days in August: On average, Perth can expect a warm day one year in five, 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 were two such days in August last year.

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 four 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) and John Cramb Western Australia Climate Services Centre
tel: (08) 9263 2222.