December weather forecastSeattle, WA
December
Weather in December
December introduces the winter season in Seattle, bringing colder temperatures and increased cloud cover. With the average lows dipping to 35.1°F (1.7°C), it is the coolest month on the calendar. This period experiences the shortest daylight hours due to the winter solstice, adding to the wintry ambiance. December captures the essence of a winter cityscape, setting the stage for festive holiday cheer. Despite the cold, the joyful spirit of the holiday season warms the heart of every Seattle resident.Temperature
Seattle experiences its lowest average temperatures in December, reaching a peak of 43.7°F (6.5°C) and a minimum of 35.1°F (1.7°C).Humidity
In December, the average relative humidity is 84%.Rainfall
The month with the most rainfall is December, when the rain falls for 8.9 days and typically aggregates up to 0.87" (22mm) of precipitation.Snowfall
April through October and December are months without snowfall.Ocean temperature
In Seattle, the average seawater temperature in December is 46.6°F (8.1°C).Note: Immersing oneself in 46.6°F (8.1°C) at sub14°F (-10°C) temperatures is a recipe for harsh cold shock and quickened breathing unless adequately equipped.
Daylight
December has the shortest days of the year, with an average of 8h and 30min of daylight.On the first day of December, sunrise is at 7:37 am and sunset at 4:19 pm. On the last day of the month, sunrise is at 7:57 am and sunset at 4:28 pm PST.
Sunshine
With an average of 4.3h of sunshine, December has the least sunshine of the year.UV index
The months with the lowest UV index are January, February, November and December, with an average maximum UV index of 2. A UV Index estimate of 2, and below, represents a minimal health vulnerability from unprotected exposure to Sun's UV rays for ordinary individuals.Note: The daily maximum UV index of 2 in December interprets into the following advice:
Extended time in the sun generally does not harm most, but those with sensitive skin, infants, and children should always be protected. Exposing oneself to the midday Sun can be harmful due to the strong UV radiation; limit your time outside. In the presence of strong sunlight, it's crucial to wear sunglasses that ward off UVA and UVB rays. Remember! The Sun's UV radiation can be magnified almost twofold by the reflection of snow.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Seattle, WA
- Average high temperature in December: 43.7°F
The warmest month (with the highest average high temperature) is August (76.3°F).
The month with the lowest average high temperature is December (43.7°F).
- Average low temperature in December: 35.1°F
The month with the highest average low temperature is August (54°F).
The coldest month (with the lowest average low temperature) is December (35.1°F).
Average pressure in December
Seattle, WA
- Average pressure in December: 30.08"Hg
The month with the highest atmospheric pressure is January (30.1"Hg).
The months with the lowest atmospheric pressure are March, August and September (30.01"Hg).
Average wind speed in December
Seattle, WA
- Average wind speed in December: 4.8mph
The windiest month (with the highest average wind speed) is March (5.3mph).
The calmest months (with the lowest average wind speed) are July and August (3.5mph).
Average humidity in December
Seattle, WA
- Average humidity in December: 84%
The month with the highest relative humidity is January (85%).
The month with the lowest relative humidity is July (69%).
Average rainfall in December
Seattle, WA
- Average rainfall in December: 0.87"
The wettest month (with the highest rainfall) is December (0.87").
The driest months (with the least rainfall) are July and August (0.12").
Average rainfall days in December
Seattle, WA
- Average rainfall days in December: 8.9 days
The month with the highest number of rainy days is November (9.1 days).
The month with the least rainy days is August (2.8 days).
Average snowfall in December
Seattle, WA
- Average snowfall in December: 0"
The month with the highest snowfall is February (0.71").
The months with the least snowfall are April, May, June, July, August, September, October and December (0").
Average snowfall days in December
Seattle, WA
- Average snowfall days in December: 0.6 days
The month with the highest number of snowfall days is February (1.9 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average sea temperature in December
Seattle, WA
- Average sea temperature in December: 46.6°F
The best month for swimming (with the highest average sea temperature) is August (53.5°F).
The coldest month (with the lowest average sea temperature) is February (45.3°F).
Average daylight in December /
Average sunshine in December
Seattle, WA
- Average daylight in December: 8h and 30min
The month with the longest days is June (Average daylight: 15h and 54min).
The month with the shortest days is December (Average daylight: 8h and 30min).
- Average sunshine in December: 4h and 18min
The month with the most sunshine is August (Average sunshine: 10h and 42min).
The month with the least sunshine is December (Average sunshine: 4h and 18min).
Average sunshine days in December
Seattle, WA
- Average sunshine days in December: 17.7 days
The month with the most sunshine days is August (25.9 days).
The month with the least sunshine days is November (16.8 days).
Average UV index in December
Seattle, WA
- Average UV index in December: 2
The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in December
Seattle, WA
- Average cloud cover in December: 56
The month with the most cloud cover is December (Cloud cover 56).
The month with the least cloud cover is August (Cloud cover 25).
Average visibility in December
Seattle, WA
- Average visibility in December: 5mi
The months with the highest visibility are April, May, June, July, August, September and October (6mi).
The months with the lowest visibility are January, February, March, November and December (5mi).
