Seattle
Autumn, winter, and early spring are frequently characterized by rain. Winters are cool and wet with December, the coolest month, averaging 40.6 degF (4.8 degC), with 28 annual days with lows that reach the freezing mark, and 2.0 days where the temperature stays at or below freezing all day; the temperature rarely lowers to 20 degF (-7 degC). Summers are sunny, dry and warm, with August, the warmest month, averaging 66.1 degF (18.9 degC), and with temperatures reaching 90 degF (32 degC) on 3.1 days per year, although 2011 is the most recent year to not reach 90 degF. The hottest officially recorded temperature was 103 degF (39 degC) on July 29, 2009; the coldest recorded temperature was 0 degF (-18 degC) on January 31, 1950; the record cold daily maximum is 16 degF (-9 degC) on January 14, 1950, while, conversely, the record warm daily minimum is 71 degF (22 degC) the day the official record high was set. The average window for freezing temperatures is November 16 thru March 10, allowing a growing season of 250 days.
What is Seattle's average December temperature? 
40.6 degF
Winters are cool and wet with December, the coolest month, averaging 40.6 degF (4.8 degC), with 28 annual days with lows that reach the freezing mark, and 2.0 days where the temperature stays at or below freezing all day; the temperature rarely lowers to 20 degF (-7 degC).
Seattle