Contents
- Weather in December
- Frequently asked questions
- Average temperature in December
- Average pressure in December
- Average wind speed in December
- Average humidity in December
- Average rainfall in December
- Average rainfall days in December
- Average snowfall in December
- Average snowfall days in December
- Average sea temperature in December
- Average daylight in December
- Average sunshine in December
- Average sunshine days in December
- Average UV index in December
- Average cloud cover in December
- Average visibility in December
Weather in December
Temperature
The month of December, characterized by an average high of 43.7°F and a low of 35.1°F, is recognized as the coldest.Humidity
In December, the average relative humidity in Seattle is 84%.Rainfall
December is the month with the most rainfall. Rain falls for 8.9 days and accumulates 0.87" of precipitation.Snowfall
April through October and December are months without snowfall in Seattle.Ocean temperature
In Seattle, in December, the average water temperature is 46.6°F.Note: Swimming in 46.6°F at temperatures under 50°F requires thermal swimsuits; otherwise, one can face cold shock and breathing difficulty. Even brief immersion at 55.4°F feels frosty.
Daylight
December has the shortest days of the year, with an average of 8h and 30min of daylight.On the first day of the month, sunrise is at 7:36 am and sunset at 4:20 pm. On the last day of December, sunrise is at 7:57 am and sunset at 4:27 pm PST.
Sunshine
December has the least sunshine of the year, with an average of 4.3h of sunshine.UV index
January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index. A UV Index reading of 2, and below, represents a low threat to health from unprotected exposure to Sun's UV rays for average individuals.Note: A maximum high daily UV index of 2 during December translates into the following directions:
Extended sunlight exposure does not pose significant problems for most people, except for children, infants, and people with fair skin who always need shielding. The Sun is most powerful around mid-day, so it's a good practice to reduce direct exposure. To mitigate harm from sun exposure, pick sunglasses offering UVA and UVB defense. Be attentive! The reflective property of snow can nearly double the Sun's UV radiation.
FAQ
What is the coldest time of year in Seattle?
How cold is December in Seattle?
What is the average humidity in December in Seattle?
What is the rainiest month in Seattle?
How many days does it rain in December in Seattle?
When it does not snow in Seattle?
Does it snow in Seattle in December?
How cold is the water in December in Seattle?
What is the month with the shortest days in Seattle?
What is the average length of the day in December in Seattle?
When is the sunrise / sunset in December in Seattle?
What is the month with the least sunshine in Seattle?
How many hours of sunshine does Seattle have in December?
What is the month with the lowest UV index in Seattle?
How high is the UV index in December in Seattle?
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 3min
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 2min
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).
Seattle, Washington, USA
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