Friday,1 May 2009 - Monthly Climate Summary for Perth - Product Code: IDCKGC11LO

Warm and dry April for Perth

Mean daily maximum temperature - well above average: Perth's mean daily maximum temperature in April was 27.6°C, which was the highest mean daily maximum temperature for 10 years, since the 28.2°C in 1999.  It also ranked as the third warmest April on record since records commenced in 1897. The average for April is 25.5°C. Daily maxima ranged from a cool 20.8°C on the 23rd to a hot 35.5°C on the 10th.

Perth's top 10 warmest Aprils
Year
Mean Maxinimum  Temperature (°C)
Departure from average
Ranking
1978
28.2
+2.7
1
1999
28.2
+2.7
1
2009
27.6
+2.1
3
1949
27.4
+1.9
4
1991
27.3
+1.8
5
1927
27.1
+1.6
6
1977
27.0
+1.5
7
1924
26.9
+1.4
8
1945
26.8
+1.3
9
1994
26.8
+1.3
9
2004
26.8
+1.3
9

Year to date mean daily maximum temperature - well above average: Perth's mean daily maximum temperature for January to April this year was 30.2°C, which was the equal second warmest such period with 1988, since the record in 1978 with 31.3°C.  The average maximum temperature for the first four months of the year is 29.0°C.

Rainfall - very much below average: The city received 5.0 mm of rainfall in April on 2 days compared with the average of 44 mm on about 7 days. This was Perth's driest April since 1994 , then 4.2 mm on 2 days, and ranked equal tenth driest April on record since records commenced in 1876. The wettest day in April 2009 was on the 14th when 4.8 mm was recorded.  Last year, Perth recorded its wettest April on record with 153.6 mm on 13 days.

Year to date rainfall - very much below average: The total rainfall for January to April this year was 20.2 mm recorded on 12 days, making it the driest such period since the 14.0 mm in 2004 and ranked tenth driest on record since records commenced in 1876. The average is 86 mm on about 16 days. Last year Perth recorded 215.4 mm on 18 days for the second wettest first four months of the year.

Mean daily minimum temperature - near average: Perth's mean daily minimum temperature in April was 13.5°C, compared with the average of 13.6°C. Daily minima ranged from a cool 6.0°C on the 23rd to a warm 20.9°C on the 13th.

April monthly mean temperature and sunshine
Element

2009

Long- term Average

Highest

Year

Lowest

Year Records Commence
Maximum
Temperature (°C)
27.6
25.5
28.2
1978/1999
21.0
1968
1897
Minimum Temperature (°C)
13.5
13.6
17.3
1978
11.6
1914
1897
Sunshine
(hours per day)
8.9
8.2
9.3
1920
4.4
1926
1898
April rainfall and rain days
Element 2009 Long-term Average Highest Year Lowest Year Records Commence
Rainfall (mm)
5.0
44
153.6
2008
0.0
3 years
1876
Rain days
2
6.9
19
1926
0
3 Years
1876
April daily extremes
Element 2009 Date Extreme Date

Records Commence

Highest daily maximum (°C)
35.5
10/04/2009
37.6
09/04/1910
1897
Lowest daily maximum (°C)
20.8
23/04/2009
13.6
16/04/1919
1897
Highest daily minimum (°C)
20.9
13/04/2009
24.4
02/04/1913
1897
Lowest daily minimum (°C)
6.0
23/04/2009
4.1
20/04/1914
1897
Wettest 24 hours to 9am (mm)
4.8
14/04/2009
69.6
17/04/2002
1876

Climate of Perth in May
Rainfall shows a dramatic increase in May as cold fronts become more frequent. The average rainfall in May is almost three times that of April. However, pleasantly mild days with cool nights also occur and on average there are almost seven hours of sunshine per day.

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

Records
Commence

Maximum temperature (°C)
22.3
24.0
2003
18.7
1931/1956
1897
Minimum temperature (°C)
10.8
13.8
1972/2005
8.8
2000
1897

Sunshine (hours per day)

6.7
7.9
2000
3.4
1905
1898
May monthly rainfall and rain days
Element
Average
Highest
Year
Lowest
Year
Records Commence
Rainfall (mm)
118
308.1
1879
14.1
1964
1876
Rain days
12.2
25
1921
5
1913
1876

Cold days in May: On average Perth has one cold day when the maximum temperature is 15°C or lower. The greatest number of such days was three in 1936. The most recent cold day Perth recorded in May was 13.0°C on 31 May 2004.

Latest 30°C day of the season: On average, Perth experiences a maximum temperature of 30°C or higher in May in six years out of ten. The latest 30°C day in the autumn season occurred on 9 May 1962, with 30.0°C.

Latest 32°C day of the season: Hot days are very rare in May with only one in every ten years on average. The latest maximum temperature of 32°C or greater occurred on 3 May 1907, with 32.2°C. 

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 (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 Perth (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.