Tuesday, 1 September 2009 - Monthly Climate Summary for Perth - Product Code: IDCKGC11LO
Warm nights and wet cloudy days for Perth in August
Rainfall - near average: The city received 111.0 mm of rainfall over 20 days in August, compared with the average of 134 mm on about 16 days. Historically, August rainfall has ranged from 11.8 mm in 1902 to 318.3 mm in 1945. The wettest day in August 2009 was the 21st when 16.2 mm was recorded.
Wet spell - the longest in 13 years:
Between the 8th and 24th August, Perth recorded 17 consecutive rain
days, which was its longest wet spell in Perth for 13 years, since the
23 consecutive rain days from the 16th July to 7th August in 1996.
Year to date rainfall - very much below average: The total rainfall for the 8-month period (January-August) this year was 483.0 mm on 71 days, which was the ninth driest January to August period on record, and the driest since the 340.4 mm on 63 days in 2006. The average for the January to August period is 685 mm on about 77 days. The total rainfall for the same period last year was 624.2 mm on 71 days.
January to August mean daily maximum temperature - third highest on record: Perth's mean daily maximum temperature for the January to August period was 25.1°C, which was the third highest mean daily maximum temperature on record. The average for the January to August period is 24.4°C. The highest mean daily maximum temperature recorded for January to August in Perth was 25.4°C in 1978.
Mean daily minimum temperature - above average: Perth's mean daily minimum temperature in August was 9.3°C, compared with the average of 8.1°C. It was the highest mean minimum temperature since the 9.7°C in 2006. Daily minima ranged from a cold 2.7°C on the 29th to a mild 14.3°C on the 14th.
Mean sunshine hours - well below average: Perth's mean sunshine hours in August was 6.1 hours, which was the least sunniest August in 25 years since the 5.7 hours in 1984. The average August sunshine hours is 7.2 hours. Last August, Perth experienced its sunniest August on record with 8.5 hours.
Climate of Perth in September
September is the first month of spring. The warming and drying trends accelerate in Perth as monthly rainfall and the number of wet days typically fall, whilst mean maximum and minimum temperatures and the number of sunshine hours increase.
Warm days in September: On average, Perth can expect two days when the maximum temperature is 25°C or higher. The record is 10 days in 1987, when the highest mean daily maximum temperature on record for September of 22.6°C was recorded.
Earliest 32-degree day of the season (hot day): The earliest 32-degree maximum temperature of the season was on the 18th September 1988, when 32.3°C was recorded, the second highest temperature for September on record.
Cold days in September: On average, Perth can expect approximately one day every five years when the maximum temperature is 15°C or lower. The record is four days in 1903 whilst there was no such day last year.
Cold nights in September: On average, Perth can expect three nights when the minimum is 5°C or lower. The record is seven nights in 2004 and there were three such nights 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 Perth (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 Perth (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.