Seattle
Washington, USA
Long-term weather forecast
Long-term weather forecast

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?

Diciembre is the coldest month in Seattle, 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 Diciembre in Seattle?

In Diciembre, in Seattle, Washington, the average high-temperature is 45.7°F (7.6°C), and the average low-temperature is 35.6°F (2°C).

What is the most humid month in Seattle?

With an average relative humidity of 80.1%, Diciembre is the most humid month in Seattle, Washington.

What is the average humidity in Diciembre in Seattle?

The average relative humidity in Diciembre in Seattle is 80.1%.

How much does it rain in Seattle in Diciembre?

In Seattle, Washington, in Diciembre, it is raining for 17.6 days, with typically 5.35" (135.9mm) of accumulated precipitation.

How many days does it snow in Diciembre in Seattle?

In Seattle, during Diciembre, snow falls for 1.6 days and regularly aggregates up to 1.7" (43.2mm) of snow.

What is the snowiest month in Seattle?

Months with the most snowfall are Febrero and Diciembre, with an average 1.7" (43.2mm) of accumulated snow.

What is the ocean temperature in Diciembre in Seattle?

In Seattle, Washington, in Diciembre, the average water temperature 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.

What is the month with the shortest days in Seattle?

With an average of 8.5h of daylight, Diciembre has the shortest days of the year in Seattle, Washington.

What is the average length of the day in Diciembre in Seattle?

In Diciembre, the average length of the day in Seattle is 8.5h.

What is the month with the least sunshine in Seattle?

The month with the least sunshine in Seattle, Washington, is Diciembre, with an average of 1.7h of sunshine.

How long on average sun shines in Diciembre in Seattle?

In Diciembre, the average sunshine is 1.7h.

When is the lowest UV index in Seattle?

Enero, Noviembre and Diciembre, with an average maximum UV index of 1, are months with the lowest UV index.

How high is the UV index in Diciembre in Seattle?

The average daily maximum UV index in Diciembre in Seattle is 1. A UV Index reading of 2, and below, represents a low health risk from the exposure to the Sun's UV rays.
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).