December weather forecast
Mount Vernon, WA

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Weather in December

December announces the onset of winter in Mount Vernon. The average temperatures hit their yearly lows, commencing at 36.3°F (2.4°C) and managing to reach only up to 42.6°F (5.9°C). Despite being the cold month, December receives 4.06" (103mm) of rainfall but also sees a slight increase in snowfall to 0.47" (12mm) over 1.5 days. The daylight duration is at its shortest leading to more cloud cover and reduced visibility. December closes the year with winter firmly set in Mount Vernon.

Temperature

The coldest period is December, when temperatures fluctuate between an average high of 42.6°F (5.9°C) and a low of 36.3°F (2.4°C).

Humidity

In Mount Vernon, the average relative humidity in December is 82%.

Rainfall

In Mount Vernon, in December, it is raining for 19.5 days, with typically 4.06" (103mm) of accumulated precipitation. In Mount Vernon, during the entire year, the rain falls for 185.2 days and collects up to 34.72" (882mm) of precipitation.

Snowfall

Months with snowfall are January through April, November and December. In December, it is snowing for 1.5 days. Throughout December, 0.47" (12mm) of snow is accumulated. In Mount Vernon, during the entire year, snow falls for 9.9 days and aggregates up to 7.91" (201mm) of snow.

Daylight

The month with the shortest days is December, with an average of 8h and 24min of daylight.
On the first day of December, sunrise is at 7:40 am and sunset at 4:16 pm. On the last day of the month, sunrise is at 8:00 am and sunset at 4:24 pm PST.

Sunshine

The month with the least sunshine is December, with an average of 3.9h 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 minimal health vulnerability from unprotected exposure to Sun's UV rays for the average person.
Note: In December, a daily maximum UV index of 2 leads to the following instructions:
The majority are not significantly affected by prolonged sun exposure. Infants, children, and those with fair skin must always have protection. Direct Sun exposure should be minimized especially during midday when radiation is most intense. To cut down UV radiation exposure by about half, sport a wide-brim hat. Remember this! The UV radiation of the Sun can be nearly doubled by the reflective properties of snow.
Updated: Jun 20, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What part of the year is the coldest?

The coldest period tends to be December, when average temperatures fluctuate between a high of 42.6°F (5.9°C) and a low of 36.3°F (2.4°C).

How cold is December?

An average high-temperature, in December, in Mount Vernon, is 42.6°F (5.9°C) and the average low-temperature is 36.3°F (2.4°C).

What is the average humidity in December?

In December, the average relative humidity in Mount Vernon is 82%.

How much does it rain in Mount Vernon in December?

In Mount Vernon, in December, during 19.5 rainfall days, 4.06" (103mm) of precipitation is typically accumulated.

How much does it snow in December?

In Mount Vernon, in December, snow falls for 1.5 days, with typically accumulated 0.47" (12mm) of snow.

What is the month with the shortest days?

With an average of 8h and 24min of daylight, December has the shortest days of the year.

What is the average length of the day in December?

In Mount Vernon, the average day length in December is 8h and 23min.

What time are sunrise and sunset in December?

On the first day of December, sunrise is at 7:40 am and sunset at 4:16 pm. On the last day of the month, sunrise is at 8:00 am and sunset at 4:24 pm PST.

What is the month with the least sunshine?

December has the least sunshine of the year, with an average of 3.9h of sunshine.

How long on average sun shines in December?

In Mount Vernon, the average sunshine duration in December is 3.9h.

What is the month with the lowest UV index?

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

What is the UV index intensity in December?

In Mount Vernon, the average daily maximum UV index in December is 2. A UV Index reading of 2, and below, represents a low health risk from unprotected exposure to 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
Mount Vernon, WA

Average temperature in December - Mount Vernon, WA
  • Average high temperature in December: 42.6°F

The warmest months (with the highest average high temperature) are July and August (68.4°F).
The month with the lowest average high temperature is December (42.6°F).

  • Average low temperature in December: 36.3°F

The month with the highest average low temperature is August (54.1°F).
The coldest month (with the lowest average low temperature) is February (36.1°F).

Average pressure in December
Mount Vernon, WA

Average pressure in December - Mount Vernon, WA
  • Average pressure in December: 30.07"Hg

The month with the highest atmospheric pressure is January (30.09"Hg).
The months with the lowest atmospheric pressure are March, August and September (30.01"Hg).

Average wind speed in December
Mount Vernon, WA

Average wind speed in December - Mount Vernon, WA
  • Average wind speed in December: 7.2mph

The windiest month (with the highest average wind speed) is November (7.5mph).
The calmest month (with the lowest average wind speed) is August (3.7mph).

Average humidity in December
Mount Vernon, WA

Average humidity in December - Mount Vernon, WA
  • Average humidity in December: 82%

The months with the highest relative humidity are January and February (83%).
The month with the lowest relative humidity is July (75%).

Average rainfall in December
Mount Vernon, WA

Average rainfall in December - Mount Vernon, WA
  • Average rainfall in December: 4.06"

The wettest month (with the highest rainfall) is November (4.96").
The driest month (with the least rainfall) is July (0.63").

Average rainfall days in December
Mount Vernon, WA

Average rainfall days in December - Mount Vernon, WA
  • Average rainfall days in December: 19.5 days

The month with the highest number of rainy days is March (20.8 days).
The month with the least rainy days is August (7.2 days).

Average snowfall in December
Mount Vernon, WA

Average snowfall in December - Mount Vernon, WA
  • Average snowfall in December: 0.47"

The month with the highest snowfall is February (3.54").
The months with the least snowfall are May, June, July, August, September and October (0").

Average snowfall days in December
Mount Vernon, WA

Average snowfall days in December - Mount Vernon, WA
  • Average snowfall days in December: 1.5 days

The month with the highest number of snowfall days is February (3.6 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).

Average daylight in December /
Average sunshine in December
Mount Vernon, WA

Average daylight in December / Average sunshine in December - Mount Vernon, WA
  • Average daylight in December: 8h and 2min

The month with the longest days is June (Average daylight: 16h and 0min).
The month with the shortest days is December (Average daylight: 8h and 24min).

  • Average sunshine in December: 3h and 5min

The months with the most sunshine are July and August (Average sunshine: 10h and 24min).
The month with the least sunshine is December (Average sunshine: 3h and 54min).

Average sunshine days in December
Mount Vernon, WA

Average sunshine days in December - Mount Vernon, WA
  • Average sunshine days in December: 9.9 days

The month with the most sunshine days is August (22.3 days).
The month with the least sunshine days is November (8.1 days).

Average UV index in December
Mount Vernon, WA

Average UV index in December - Mount Vernon, WA
  • Average UV index in December: 2

The month with the highest UV index is 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
Mount Vernon, WA

Average cloud cover in December - Mount Vernon, WA
  • Average cloud cover in December: 59

The month with the most cloud cover is December (Cloud cover 59).
The month with the least cloud cover is August (Cloud cover 26).

Average visibility in December
Mount Vernon, WA

Average visibility in December - Mount Vernon, WA
  • Average visibility in December: 6mi

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

Mount Vernon, Washington, USA

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