Wednesday 4 October, 2006

MONTHLY CLIMATE SUMMARY - WESTERN AUSTRALIA REGIONAL OFFICE

Close to average September for Perth

September Rainfall - near average: The city received 86.4 mm of rainfall over 17 days in September compared with the average of 81 mm over 15 days. The wettest day in September 2006 was the 11th when 22.0 mm was recorded. Last September Perth registered 91.0 mm on 17 days.

Nine-monthly rainfall - very much below average: The total rainfall for January to September this year was 426.8 mm on 80 days making it the second driest such period on record for Perth. The driest was 421.4 mm on 83 days in 1914. The average is 771 mm.

Perth's top 10 driest years to date (January to September total)
Season	Rainfall (mm)	Rain Days	Ranking
1914	421.4	83	1
2006	426.8	80	2
1940	432.2	76	3
1877	497.9	87	4
1979	501.2	89	5
1977	503.2	75	6
1959	514.0	93	7
1894	522.0	84	8
1969	530.2	79	9
1911	553.6	87	10

Mean daily maximum temperature - near average: Perth's mean daily maximum temperature in September was 20.6°C compared with the average 20.0°C. Daily maxima ranged from a cool 16.4°C on the 1st to a warm 30.5°C on the 29th, the warmest daily maximum temperature for September for twelve years.

Mean daily minimum temperature - near average: Perth's mean daily minimum temperature in September was 10.0°C, compared with the average of 9.4°C. Daily minima ranged from a cold 3.7°C on the 2nd to a mild 15.4°C on the 10th.

September monthly mean temperature and sunshine
Element	2006	Long- term Average	Highest	Year	Lowest	Year	Records Commence
Maximum Temperature (°C)	20.6	20.0	22.6	1987	16.8	1915	1897
Minimum Temperature (°C)	10.0	9.4	12.4	1988	8.0	2004	1897
Sunshine (hours per day)	7.9	7.7	8.8	Many	4.2	1907	1898
September rainfall and rain days
Element	2006	Long-term Average	Highest	Year	Lowest	Year	Records Commence
Rainfall (mm)	86.4	81	199.1	1923	8.7	1916	1876
Rain days	17	15	26	1915	4	1877	1876

September daily extremes
Element	2006	Date	Extreme	Date	Records Commence
Highest daily maximum (°C)	30.5	29/09/2006	32.7	30/09/1918	1897
Lowest daily maximum (°C)	16.4	01/09/2006	11.4	17/09/1917	1897
Highest daily minimum (°C)	15.4	10/09/2006	19.5	08/09/1916	1897
Lowest daily minimum (°C)	3.7	02/09/2006	1.5	* Twice	1897
Wettest 24 hours to 9am (mm)	22.0	11/09/2006	51.8	14/09/1984	1876

* Denotes the lowest minimum temperature for September on record on the following dates: 1 and 10 September 2005.

Climate of Perth in October

October days are generally mild, with more frequent sunshine and some warm to hot days. There is typically a marked reduction in rainfall compared with September. The October rainfall average is 53 mm on 9 days.

October monthly mean temperatures and sunshine
Element	Average	Highest	Year	Lowest	Year	Records Commence
Maximum temperature (°C)	22.7	25.8	1969	18.8	1924	1897
Minimum temperature (°C)	11.1	14.2	1969	9.3	1910	1897
Sunshine (hours per day)	9.6	10.9	2000	5.5	1898	1898
October rainfall and rain days
Element	Average	Highest	Year	Lowest	Year	Records Commence
Rainfall (mm)	53	199.9	1890	1.0	1969	1876
Rain days	9	22	1898	1	1969	1876

October daily extremes
Element	Highest	Date	Lowest	Date	Records Commence
Maximum temperature (°C)	37.3	29/10/1967	11.9	08/10/1932	1897
Minimum temperature (°C)	22.2	29/10/1979	2.2	06/10/1994	1897
Rainfall 24 hours to 9am (mm)	68.2	18/10/1995	n/a	n/a	1876

Hot days in October: On average, Perth has one hot day when the maximum temperature is 32 degrees or higher. The greatest number of such days in October was four in 1969. The last time Perth recorded an October day over 32 degrees was in 2000, with 34.2 degrees on the 28th.

Earliest 35-degree day of the season: The earliest 35-degree maximum temperature of the season was on 20 October 1996 when 36.9 degrees was recorded, the fourth highest maximum temperature for October on record.

Cold nights in October: On average, Perth can expect one cold night when the minimum temperature is 5 degrees or less. There were two such nights in October 2005.

October top 10 hottest			October top 10 coldest
Position	Date	Max temp °C	Position	Date	Max temp°C
1	29 October 1967	37.3	1	08 October 1932	11.9
2	26 October 1961	37.2	2	17 October 1924	12.7
3	29 October 1979	37.1	3	18 October 1947	13.0
4	20 October 1996	36.9	4	05 October 1968	13.1
5	30 October 1988	36.3	5	09 October 1903	13.7
6	26 October 1972	36.2	6	02 October 1933	14.2
7	24 October 1960	35.9	7	03 October 1962	14.3
8	25 October 1961	35.6	7	05 October 1965	14.3
9	30 October 1922	35.2	9	08 October 1956	14.4
9	24 October 1981	35.2	10	01 October 1947	14.6

October top 10 warmest			October top 10 coldest
Position	Date	Mix temp °C	Position	Date	Min temp°C
1	29 October 1979	22.2	1	06 October 1994	2.2
2	13 October 1991	21.3	2	10 October 2005	2.5
3	20 October 1967	21.0	3	11 October 1996	4.0
4	03 October 1963	20.4	3	11 October 2005	4.0
4	22 October 1977	20.4	5	06 October 1968	4.2
6	31 October 1922	19.9	5	07 October 1994	4.2
6	21 October 1994	19.9	7	10 October 2001	4.3
8	25 October 1983	19.7	7	18 October 2003	4.3
9	15 October 1970	19.5	9	16 October 1931	4.4
10	29 October 1900	19.4	10	02 October 2004	4.5
10	31 October 1936	19.4	-	-	-
10	10 October 1991	19.4	-	-	-

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 Glenn Cook Western Australia Climate Services Centre