Seattle Weather in December
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 temperature, precipitation, sun, humidity, wind and storms for Seattle. The weather measurements are averages based on climate data gathered at Seattle — Tacoma International Airport, located south of the city center.
|47 °F||December average high||8 °C|
|38 °F||December average low||3 °C|
December is the coldest month for Seattle and overall the 19th and 27th are its chilliest days. They have daily highs averaging 46 degrees Fahrenheit (8 degrees Celsius) and lows of 37 °F (3 °C).
|9 days||50 °F max. or more (10 °C)|
|23 days||40 °F min. or less (4 °C)|
Nearly every December day warms to over 40 °F (4 °C) in Seattle. Temperatures above 60 °F (16 °C) are uncommon here this month. Typically one entire day during December remains below freezing.
The thermometer dips to freezing or below on an average of 7 nights this month. But it's unusual for December to get as cold as 20 °F (-8 °C).
|5.7 in||total precipitation||145 mm|
|18 days||of rain or snowfall|
Half the time, the Seattle receives 3.9 to 7.2 inches (100 to 183 mm) of precipitation for December. One in four years has drier weather, while another one in four is wetter.
|1.7 in||total snowfall||4 cm|
|2 days||with new snow|
Most Decembers remain free of snow. Only in one out of four years does the city receive 1.1 inches (3 cm) or more of snow for the month.
|3 days||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.
|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 Time||1 am||4 am||7 am||10 am||1 pm||4 pm||7 pm||10 pm|
|9.5 mph||December wind speed average||15.3 kph|
December is one of the windiest months in Seattle.
|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.
The weather data here are long-term averages provided by the US National Centers for Environmental Information (NCEI). Temperature and precipitation are 1991-2020 normals while humidity and thunderstorms are 1961-1990 normals.