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.

Perth's top 10 driest Octobers
Year
Rainfall (mm)
Rain Days
Rank
1969
1.0
1
1
1946
3.8
4
2
2000
5.2
6
3
2009
6.8
7
4
1892
12.4
5
5
1881
13.3
5
6
1877
13.7
11
7
1983
14.0
3
8
1944
14.9
10
9
1994
15.8
6
10

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.

Perth's top 10 driest years to date
(January to October)
Year
Rainfall mm
Rain Days
Rank
2006
445.4
87
1
1914
458.5
94
2
1940
493.2
89
3
1877
511.6
98
4
1979
529.8
100
5
1969
531.2
79
6
1894
559.7
95
7
1959
567.4
106
8
2009
570.0
104
9
1911
579.3
96
10

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.

Perth Top 4 hottest days in October
Date
Max Temp°C
Rank
29/10/1967
37.3
1
26/10/1961
37.2
2
29/10/1979
37.1
3
20/10/1996
36.9
4
17/10/2009
36.9
4

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. 

October monthly mean temperature and sunshine
Element

2009

Long- term Average

Highest

Year

Lowest

Year Records Commence
Maximum
Temperature (°C)
23.3
22.9
25.8
1969
18.8
1924
1897
Minimum
Temperature (°C)
12.3
11.2
14.2
1969
9.3
1910
1897
Sunshine
(hours per day)
9.5
9.6
10.9
2000
5.5
1898
1898
October rainfall and rain days
Element 2009 Long-term Average Highest Year Lowest Year Records Commence
Rainfall (mm)
6.8
53
199.9
1890
1.0
1969
1876
Rain days
7
9.2
22
1898
1
1969
1876

October daily extremes
Element 2009 Date Extreme Date

Records Commence

Highest daily maximum (°C)
36.9
17/10/2009
37.3
29/10/1967
1897
Lowest daily maximum (°C)
17.5
11/10/2009
11.9
08/10/1932
1897
Highest daily minimum (°C)
19.0
17/10/2009
22.2
29/10/1979
1897
Lowest daily minimum (°C)
4.3
01/10/2009
2.2
06/10/1994
1897
Wettest 24 hours to 9am (mm)
3.4
11/10/2009
68.2
18/10/1995
1876

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.

November monthly mean temperatures and sunshine
Element Average Highest Year Lowest Year

Records
Commence

Maximum
Temperature (°C)
26.2
28.5
2007
21.5
1971
1897
Minimum
Temperature (°C)
14.1
16.9
1982
11.9
1954
1897

Sunshine
(hours per day)

10.7
12.3
2007
5.1
1965
1898
November rainfall and rain days
Element
Average
Highest
Year
Lowest
Year
Records Commence
Rainfall (mm)
22
73.2
1984
0.0
1891
1876
Rain days
6.4
14
3 years
0
1891
1876

November daily extremes
Element
Highest
Date
Lowest
Date
Records Commence
Maximum temperature (°C)
40.3
** Twice
15.8
02/11/1919
1897
Minimum temperature (°C)
25.1
24/11/1920
5.0
18/11/2004
1897
Rainfall 24 hours to 9am (mm)
39.1
29/11/1956
n/a
n/a
1876

** 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.