December weather forecast and climate
Seattle, WA

Beautiful dusk skyline over the giant skyscrapers of Seattle, Washington
Beautiful dusk skyline over the giant skyscrapers of Seattle, Washington
Winter sets in December with the highest humidity of 81% and extremely low temperatures in the range of 35.6°F (2°C) and 46.4°F (8°C) making Seattle cold and an icy city with the constantly blowing winds.
Snowing increases to an average of two days to accumulate 1.7" (43.2mm) of snow in December. The nights become colder and almost unbearable as temperatures occasionally drop to 32°F (0°C).
December is the rainiest month of the year with the rain gauge collecting precipitation of up to 6.1" (154.9mm) across nineteen days of heavy rainfall. Flooding may occur, albeit lightly, and precaution is advised.
Sea activities are halted as the sunshine hours drop to a weak two, and the waters become freezing cold 46.4°F (8°C).

What is the coldest month in Seattle?

December is the coldest month in Seattle, Washington, with an average high-temperature of 45.7°F (7.6°C) and an average low-temperature of 35.6°F (2°C).

What is the temperature in December in Seattle?

The average high-temperature, in December, is 45.7°F (7.6°C), while the average low-temperature is 35.6°F (2°C).

How much does it rain in Seattle in December?

In Seattle, Washington, in December, it is raining for 17.6 days, with typically 5.4" (135.9mm) of accumulated precipitation.

How much does it snow in Seattle in December?

In December, in Seattle, Washington, it is snowing for 1.6 days. Throughout December, 1.7" (43.2mm) of snow is accumulated.

When does it snow the most in Seattle?

Months with the most snowfall in Seattle are February and December, with an average 1.7" (43.2mm) of accumulated snow.

What is the sea water temperature in December in Seattle?

The average seawater temperature, in December, is 46.6°F (8.1°C). Swimming in 46.6°F (8.1°C) is considered dangerous. Unprotected immersion in temperatures below 50°F (10°C) causes quickly maximum intensity cold shock with hyperventilation.
Average temperature in December - Seattle, WA
  • Average high temperature in December: 45.7°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 (45.7°F).

  • Average low temperature in December: 35.6°F

The month with the highest average low temperature is August (55.9°F).
The coldest month (with the lowest average low temperature) is December (35.6°F).

Average humidity in December - Seattle, WA
  • Average humidity in December: 80.1%

The month with the highest relative humidity is December (80.1%).
The month with the lowest relative humidity is July (65.4%).

Average rainfall in December - Seattle, WA
  • Average rainfall in December: 5.4"

The wettest month (with the highest rainfall) is November (6.6").
The driest month (with the lowest rainfall) is July (0.7").

Average rainfall days in December - Seattle, WA
  • Average rainfall days in December: 17.6 days

The month with the highest number of rainy days is November (18.4 days).
The month with the lowest number of rainy days is August (4.8 days).

Average snowfall in December - Seattle, WA
  • Average snowfall in December: 1.7"

Months with the highest snowfall are February and December (1.7").
Months with the lowest snowfall are April, May, June, July, August, September and October (0").

Average snowfall days in December - Seattle, WA
  • Average snowfall days in December: 1.6 days

The month with the highest number of snowfall days is December (1.6 days).
Months with the lowest number of snowfall days are April, 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: 8.5h

The month with the longest days is June (Average daylight: 15.9h).
The month with shortest days is December (Average daylight: 8.5h).

  • Average sunshine in December: 1.7h

The month with most sunshine is July (Average sunshine: 10.1h).
The month with least sunshine is December (Average sunshine: 1.7h).

Average UV index in December - Seattle, WA
  • Average UV index in December: 1

Months with the highest UV index are June and July (UV index 7).
Months with the lowest UV index are January, November and December (UV index 1).

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