Seattle Weather in December

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December brings the worst of winter weather to Seattle, Washington. This is the city's coldest and snowiest month. Still, most nights don't freeze and most Decembers never see snow.

This page gives detailed information on the typical December weather for Seattle. You can jump directly to data and descriptions for:

The temperature, precipitation and sunshine numbers here are historical averages based on climate data gathered at Seattle's Husky Stadium, located near downtown Seattle at the University of Washington on the shore of Lake Washington's Union Bay. The rest of the measurements are averages from the Seattle - Tacoma International Airport, located south of the city center.

temperature iconTemperature

47 °F December average high 8 °C
36 °F December average low 2 °C

In most years, Seattle averages a daily maximum temperature for December that's between 45 and 49 degrees Fahrenheit (7 to 9 degrees Celsius). The minimum temperature usually falls between 34 and 38 °F (1 to 3 °C).

December is the coldest month overall for Seattle and the 20th and 21st are its chilliest days. They have daily highs averaging 46.2 °F (7.9 °C) and lows of 35.6 °F (2.0 °C).

9 days 50 °F maximum or above (10 °C)
23 days 40 °F minimum or below (4 °C)

Nearly every December day warms to over 40 °F (4 °C) in Seattle. Temperatures above 60 °F (16 °C) are not expected here this month. Typically one entire day during December remains below freezing.

The thermometer dips to freezing or below on an average of 8 nights. But it's unusual for December to get as cold as 20 °F (-8 °C).

precipitation iconPrecipitation

6.1 inches total December precipitation 154 millimetres
17 days of rain or snowfall

December is Seattle's rainiest month. Half the time, the city receives 5 to 8 inches (115 to 198 mm) of precipitation for the month. One in four years has drier weather, while another one in four is wetter.

snowfall iconSnow

2.5 inches total December snowfall 6.4 centimetres
1 day with new snow

Although this is Seattle's snowiest month of winter on average, most Decembers remain free of snow. Only in one out of four years does the city receive 1.5 inches (4 cm) or more of snow for the month.

sunshine iconSun

23 % sunshine in December
3 days with clear skies

The sun's rays reach the ground in Seattle during 23 percent of daylight hours on average in December, for a total of 60 hours in the month. Typically on 3 days this month the sky is mainly clear, with at most 30 percent cloud cover.

Sunlight in December at Seattle averages 8 hours and 29 minutes a day. The shortest days of the year, from around December 20th to 22nd, last 8 hours and 25 minutes from sunrise to sunset.

humidity iconHumidity

80 % December average humidity

The relative humidity in Seattle during December usually peaks at 83 percent in the morning then drops to 76 percent by early afternoon.

Local Time1 am4 am7 am10 am1 pm4 pm7 pm10 pm
Humidity % 81 82 83 81 76 77 80 80

wind iconWind

9.5 mph December wind speed average 15.3 kph

December is one of the windiest months in Seattle.

lightning cloud iconStorms

4 days rainfall of 0.5 inches (13 mm) or more
0 days with thunderstorms in December

December is among the stormiest of months for Seattle. A December storm in Seattle usually means heavy rain and only rarely snow.

The city has a December thunderstorm on an average of once every few years.

Reference

These weather data are long-term historical averages provided by the National Climatic Data Center of the United States. The temperature and precipitation numbers are 1981-2010 normals while the humidity and thunderstorm statistics are 1961-1990 normals.

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