Wednesday, 1 June 2011 - Monthly Climate Summary for Sydney - Greater Sydney - Product code IDCKGC25L0

Sydney in May 2011: Coldest nights in 40 years

• Above average rainfall
• Wettest May day since 2003
• Coldest minimum temperatures since 1970
• Coldest maximum temperatures since 1979

Extremes Records Summaries Important notes the top

Rainfall

Sydney Observatory Hill recorded 135.6 mm of rainfall during May 2011, slightly above the historical average of 121.2 mm although drier than May 2010. The majority of the rain fell during the last two days of the month, as a coastal low pressure trough with an upper low in northern NSW caused a two-day total of 101.2 mm at Observatory Hill. Rain was particularly heavy on the 31st, reaching 65.2 mm at Observatory Hill, the wettest May day since 2003, and 103.4 mm at Parramatta North. This event was associated with flash flooding in Sydney on the 30th, particularly in southern suburbs near the Airport.

The remainder of the month was fairly dry, associated with generally cool, dry southwesterly winds. Only 11 rain days were observed at Observatory Hill during the month, below the May average of 13 rain days, the majority of which recorded less than 5 mm. The only other significant rain event occurred between the 25th and 26th, with two-day totals of 21.4 mm at Observatory Hill and up to 50 mm at Rose Bay and Dover Heights. This event was associated with an East Coast Low off the NSW coast, which are typical for late autumn and winter in Sydney.

Temperature

Sydney Observatory Hill recorded slightly above average maximum temperatures during May, averaging 19.5 °C compared to the historical average of 19.4 °C, although significantly below the 1961-1990 average of 20.3 °C. This is the coolest May for maximum temperatures since 18.9 °C was recorded in May 1979, reflecting more than thirty consecutive years of above average maximum temperatures. In comparison, most of the Metropolitan area had average maximum temperatures close to 1 °C below their historical average, based on records generally beginning in the 1960s.

Minimum temperatures were colder during May, with an average minimum temperature at Observatory Hill of 10.7 °C compared to the historical average of 11.5 °C. This is the lowest minimum temperature since 10.4 °C was recorded in May 1970. Interestingly, average minimum temperatures less than or equal to 10.7 °C were recorded 19 times at Observatory Hill between 1910 and 1970, with such temperatures typical of the early part of the 20th century. In comparison, the majority of stations in western Sydney had temperatures close to 2 °C below the historical average, including the coldest May on record at Prospect Reservoir.

Some sites had their lowest May mean daily minimum temperature on record.

Wind

The average wind direction at Sydney Airport during May was westerly to southwesterly, with more than 90% of 9am winds between NW and SW, and 55% of 3pm winds between S and W. This was a larger proportion than typical for May, with the southwesterly winds driving cool conditions during the month.

Eight strong wind days were reported at Sydney Airport, well above average for May and the highest frequency since 9 strong wind days were reported in May 1972. The windiest days were the 25th, when an East Coast Low caused wind gusts of up to 91 km/hr at Port Botany, and on the 30th as a strong low pressure trough and upper level low caused wind gusts of up to 94 km/hr at Fort Denison.

Other phenomena

Sydney Airport averaged 6.8 hours of sunshine during May, above the historical average of 6.1 hours. No thunderstorms were reported at the Airport, below average for May, with five storms reported in the Metropolitan region during the month.

Extremes Records Summaries Important notes the top

Extremes Records Summaries Important notes the top

Extremes Records Summaries Important notes the top

Most values are the precipitation in the 24 hours to 9 am on the day indicated. Days marked with »» are part of a longer accumulation, which is marked like this on the final day. Values over 100 mm have been rounded to the nearest whole millimetre. Days marked with - have a rainfall report of zero; days left blank have no rainfall report (which often indicates no rain fell).
This table is very wide; you may have to scroll sideways to see all the days, and you may need to set the paper to 'landscape' to print.

Extremes Records Summaries Important notes the top