December 2011 was a wet, cloudy and unusually cool month.
The rainfall total of 111.6 millimetres was 23 mm higher than the average with a number of moderate to heavy falls resulting in local flooding - see details below.
Numerous cloudy days along with cool easterly winds kept daytime temperatures down to record breaking low levels. The average maximum of 20.7C was the lowest on record for December from 147 years of available records. The previous lowest was 21.6C in 1927 (figure adjusted for site difference) .
Temperatures failed to reach the December long term average of 25.0C, the highest for the month was just 24.9C on the 26th.
Despite the wet conditions, thunderstorm activity was lower than normal with storms on three days. There was no hail with any of these storms.
Winds were mostly light to moderate easterlies.

Noteworthy events:

1st - A trough moving through New South Wales brought moderate rain throughout the morning and early afternoon totaling 24.4 mm. As the ground was already saturated from a rain event a week earlier, moderate flooding occurred in Dumaresq Creek during the afternoon and evening. The waters gradually subsided the following day, the 2nd, but several streets within the city remained closed until the afternoon.

1st-7th - Cloudy, rainy conditions and chilly easterly winds kept maximum temperatures to unusually low levels for the first week of summer. The average maximum for the seven days was just 17.2C ranging from 14.0C to 22.4C. This was the coldest first week of December for at least 72 years (daily records are only available from 1939). The long term average maximum temperature in early December is 24C. The maximums of 14.4C on the 5th, and 14.0C on the 7th were the lowest for December since 6th December 2003 (13.5C).
22nd - Another trough produced moderate to heavy rain in the afternoon and evening totaling 31.2 mm resulting in minor to moderate flooding in Dumaresq Creek in the late evening and throughout the following day.

DECEMBER STATISTICS  (long term averages in brackets):

Rainfall:  111.6 mm  (88.8 mm)

Rain days:  14  (10)
2011 rainfall total:  1,048.0 mm  (787.3 mm)

Average maximum temp:  20.7 deg  (25.0 deg)   

Average minimum temp:  10.6 deg  (11.1 deg)   

Highest maximum temp:  24.9 deg on the 26th

Lowest maximum temp:  14.0 deg on the 7th

Highest minimum temp:  14.3 deg on the 22nd

Lowest minimum temp:  6.5 deg on the 29th

Fine sunny days:  6  (16)

Ideal weather days:  0  (0.4)

Days with thunderstorms:  3  (8)

Days with frosts:  0  (0.3)    

Days with fogs:  4  (1)

Wind direction at 3pm & number of days:  E: 19,  W: 4,  SW: 4,  SE: 2,  S: 1,  NW: 1

Average daily evaporation:  3.6 mm  (5.2 mm)

Thunderstorm details:

12th:   1.00pm - slight storm - 2.0 mm rain
21st:   2.00-3.15pm - slight storm from west
27th:   2.35-2.45pm - thunder heard in east - no rain