Monday, 2 November 2009 - Monthly Climate Summary for Perth - Product Code: IDCKGC11LO

Fourth driest October on record for Perth

Rainfall - well below average: The city received 6.8 mm of rainfall over 7 days in October 2009, which was the fourth driest October on record and the driest October since the 5.2 mm in 2000.

Year to date rainfall - well below average: The total rainfall for January to October this year was 570.0 mm on 104 days which was the ninth driest such period on record and the driest since 2006 when 445.4 mm on 87 days was observed. The long-term average rainfall for January to October is 819 mm on about 101 days. The total for the same period last year was 738.4 mm on 97 days.

Mean daily maximum temperature - near average: Perth's mean daily maximum temperature in October was 23.3°C, compared with the average of 22.9°C. Daily maxima ranged from a mild 17.5°C on the 11th to a hot 36.9°C on the 17th (see below). 

Earliest 35°C day of the season: On 17th October 2009, Perth recorded a maximum temperature of
36.9°C, which was the hottest October day for 13 years and the equal fourth hottest October day on record. It was also the earliest 35°C or more day of the season on record. The previous record has occurred on two occasions: 20th October 1996 with 36.9°C and 20th October 2008 with 35.7°C.

Mean daily minimum temperature - above average: Perth's mean daily minimum temperature in October was 12.3°C, which was the highest mean daily minimum temperature on record for the Perth Metro site (Mount Lawley) since records commenced in November 1993. The average for October is 11.2°C. Daily minima ranged from a cold 4.3°C on the 1st to a warm 19.0°C on the 17th. 

Climate of Perth in November

November days in Perth are generally sunny and either mild or warm. A few hot days occur, usually in the latter part of the month. The general springtime decline in rainfall continues with an average of 22 mm over about six days.

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

Hot days in November: On average, Perth can expect four days when the maximum temperature is 32°C or higher. The record of nine such days was set in 1940,whilst last November Perth recorded no such days.

Earliest 40°C day of the season: The earliest 40°C maximum temperature of the season occurred on 11 November 2003, when 40.3°C was recorded. A maximum temperature of 40°C or higher has only occurred three times in November in Perth since records began in 1897.

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 Mount 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 Mount 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 Yanhui Blockley Western Australia Climate Services Centre
on, tel: (08) 9263 2222, office hours.