December weather forecast
Sammamish, WA

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Dense pine tree cover and houses in the town of Sammamish, Washington, in the Pine Lake area
Dense pine tree cover and houses in the town of Sammamish, Washington, in the Pine Lake area

Weather in December

December marks the pinnacle of winter in Sammamish, characterised by the year’s lowest average temperature, falling to 33.6°F (0.9°C). The season brings forth a mild amount of snowfall, with the city receiving 0.35" (9mm) in December, creating a white winter spectacle. The increase in relative humidity to 85% indicates higher moisture content in the atmosphere, in line with the winter season. The daylight hours are at their shortest in December, while the pressure reaches its yearly peak of 30.09 in. Despite the cold, the festive spirit of the city sparkles through making it a prime attraction for holiday travelers.

Temperature

The month of December sees the lowest average temperatures, reaching 42.3°F (5.7°C) at the peak and 33.6°F (0.9°C) at the low.

Humidity

January, February and December, with an average relative humidity of 85%, are the most humid months.

Rainfall

December is the month with the most rainfall. Rain falls for 14.1 days and accumulates 1.85" (47mm) of precipitation.

Snowfall

Months with snowfall are January through April, November and December. In Sammamish, Washington, during December, snow falls for 1.3 days and regularly aggregates up to 0.35" (9mm) of snow. Throughout the year, there are 9.3 snowfall days, and 3.27" (83mm) of snow is accumulated.

Daylight

With an average of 8h and 30min of daylight, December has the shortest days of the year.
On the first day of the month, sunrise is at 7:36 am and sunset at 4:18 pm. On the last day of December, sunrise is at 7:56 am and sunset at 4:26 pm PST.

Sunshine

The months with the least sunshine are January and December, with an average of 4.2h 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 value of 2, and less, symbolizes a low health risk from unsafe exposure to UV radiation for ordinary individuals.
Note: A maximum high UV index of 2 in December translates into the following recommendations:
Extended sun exposure is not an issue for the majority. Children, infants, and fair-skinned individuals always need to be protected. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. On sunny days, it's ideal to wear sunglasses that filter out UVA and UVB rays. Pay attention! The reflection of snow can enhance the Sun's UV radiation almost double.
Updated: Aug 31, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What part of the year is the coldest?

December, recording an average high temperature of 42.3°F (5.7°C) and a low temperature of 33.6°F (0.9°C), is Sammamish's coldest month.

Is it cold in Sammamish during December?

The high-temperature, in December, in Sammamish, is 42.3°F (5.7°C), while the low-temperature averages to 33.6°F (0.9°C).

What is the most humid month?

January, February and December, with an average relative humidity of 85%, are most humid months.

What is the average humidity in December?

The average relative humidity in December is 85%.

What is the wettest month?

The month with the most rainfall is December, when the rain falls for 14.1 days and typically aggregates up to 1.85" (47mm) of precipitation.

How much does it rain in December?

In December, the rain falls for 14.1 days. Throughout December, 1.85" (47mm) of precipitation is accumulated.

How much does it snow in December?

In Sammamish, in December, during 1.3 snowfall days, 0.35" (9mm) of snow is typically accumulated.

What is the month with the shortest days?

December has the shortest days of the year, with an average of 8h and 30min of daylight.

What is the average length of the day in December?

In Sammamish, the average day length in December is 8h and 30min.

When is the sunrise / sunset in December?

On the first day of December, sunrise is at 7:36 am and sunset at 4:18 pm. On the last day of the month, sunrise is at 7:56 am and sunset at 4:26 pm PST.

What is the month with the least sunshine?

January and December, with an average of 4.2h of sunshine, are months with the least sunshine in Sammamish.

How many hours of sunshine does Sammamish have in December?

The average sunshine duration in December is 4.2h.

When is the lowest UV index?

January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index.

What is the UV index intensity in December?

The average daily maximum UV index in December is 2. A UV Index estimate of 2, and below, represents a minimal health vulnerability from exposure to the Sun's UV radiation.
Average humidity
Average rainfall days
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in December
Sammamish, WA

Average temperature in December - Sammamish, WA
  • Average high temperature in December: 42.3°F

The warmest month (with the highest average high temperature) is August (76.5°F).
The month with the lowest average high temperature is December (42.3°F).

  • Average low temperature in December: 33.6°F

The month with the highest average low temperature is August (52.2°F).
The coldest month (with the lowest average low temperature) is December (33.6°F).

Average pressure in December
Sammamish, WA

Average pressure in December - Sammamish, WA
  • Average pressure in December: 30.09"Hg

The month with the highest atmospheric pressure is January (30.1"Hg).
The month with the lowest atmospheric pressure is August (30"Hg).

Average wind speed in December
Sammamish, WA

Average wind speed in December - Sammamish, WA
  • Average wind speed in December: 4.6mph

The windiest month (with the highest average wind speed) is January (5mph).
The calmest month (with the lowest average wind speed) is August (3.4mph).

Average humidity in December
Sammamish, WA

Average humidity in December - Sammamish, WA
  • Average humidity in December: 85%

The months with the highest relative humidity are January, February and December (85%).
The month with the lowest relative humidity is July (70%).

Average rainfall in December
Sammamish, WA

Average rainfall in December - Sammamish, WA
  • Average rainfall in December: 1.85"

The wettest month (with the highest rainfall) is December (1.85").
The driest months (with the least rainfall) are July and August (0.35").

Average rainfall days in December
Sammamish, WA

Average rainfall days in December - Sammamish, WA
  • Average rainfall days in December: 14.1 days

The month with the highest number of rainy days is March (14.8 days).
The month with the least rainy days is August (5.2 days).

Average snowfall in December
Sammamish, WA

Average snowfall in December - Sammamish, WA
  • Average snowfall in December: 0.35"

The month with the highest snowfall is February (1.38").
The months with the least snowfall are May, June, July, August, September and October (0").

Average snowfall days in December
Sammamish, WA

Average snowfall days in December - Sammamish, WA
  • Average snowfall days in December: 1.3 days

The month with the highest number of snowfall days is February (3.2 days).
The months with the least snowfall days are May, June, July, August and October (0 days).

Average daylight in December /
Average sunshine in December
Sammamish, WA

Average daylight in December / Average sunshine in December - Sammamish, 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 1min

The month with the most sunshine is August (Average sunshine: 10h and 42min).
The months with the least sunshine are January and December (Average sunshine: 4h and 12min).

Average sunshine days in December
Sammamish, WA

Average sunshine days in December - Sammamish, WA
  • Average sunshine days in December: 15.2 days

The month with the most sunshine days is August (24 days).
The month with the least sunshine days is November (13.5 days).

Average UV index in December
Sammamish, WA

Average UV index in December - Sammamish, WA
  • Average UV index in December: 2

The months with the highest UV index are June and July (UV index 5).
The months with the lowest UV index are January, February, November and December (UV index 2).

Average cloud cover in December
Sammamish, WA

Average cloud cover in December - Sammamish, WA
  • Average cloud cover in December: 57

The month with the most cloud cover is December (Cloud cover 57).
The month with the least cloud cover is August (Cloud cover 26).

Average visibility in December
Sammamish, WA

Average visibility in December - Sammamish, WA
  • Average visibility in December: 5mi

The months with the highest visibility are June, July, August and September (6mi).
The months with the lowest visibility are January, February, March, April, May, October, November and December (5mi).

Sammamish, Washington, USA

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