December weather forecast
Grand Coulee, WA

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Weather in December

December, the first month of the winter in Grand Coulee, is also a subzero cold month, with an average temperature fluctuating between 31.6°F (-0.2°C) and 21.4°F (-5.9°C).

Temperature

December, with its average high-temperature of 31.6°F (-0.2°C) and an average low-temperature of 21.4°F (-5.9°C), holds the record as the coldest month.

Humidity

In Grand Coulee, the average relative humidity in December is 86%.

Rainfall

The wettest months in Grand Coulee are May and December, with an average 1.18" (30mm) of rainfall.

Snowfall

Months with snowfall are January through April, September through December. In Grand Coulee, in December, snow falls for 10.5 days, with typically accumulated 3.78" (96mm) of snow. Throughout the year, there are 33.4 snowfall days, and 14.65" (372mm) of snow is accumulated.

Daylight

December has the shortest days of the year in Grand Coulee, with an average of 8h and 30min of daylight.
On the first day of the month, sunrise is at 7:25 am and sunset at 4:05 pm. On the last day of December, sunrise is at 7:45 am and sunset at 4:13 pm PST.

Sunshine

In December, the average sunshine is 4.4h.

UV index

The average daily maximum UV index in December in Grand Coulee is 2. A UV Index reading of 2, and below, represents a low health risk from exposure to the Sun's UV rays for ordinary individuals.
Note: In December, a regular UV index of 2 translates into these guidelines:
Infants, children, and people with sensitive skin should always have protection against lengthy periods of sun exposure. The Sun's most harmful UV rays are emitted around midday; avoid staying outdoors for long during this time. During bright days, sunglasses that offer UVA and UVB defense are recommended. Mark this! Snow reflection can nearly double the UV radiation intensity from the Sun.
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Frequently asked questions

What time of the year is the coldest in Grand Coulee?

Grand Coulee's December weather, with an average high temperature of 31.6°F (-0.2°C) and an average low temperature of 21.4°F (-5.9°C), tends to be the coldest of the year.

How cold is December in Grand Coulee?

December temperatures in Grand Coulee vary between a high-temperature of 31.6°F (-0.2°C) and a low-temperature of 21.4°F (-5.9°C).

What is the average humidity in December in Grand Coulee?

The average relative humidity in December is 86%.

What is the rainiest month in Grand Coulee?

The wettest months in Grand Coulee, Washington, are May and December, with an average 1.18" (30mm) of rainfall.

How many days does it rain in December in Grand Coulee?

In December, in Grand Coulee, Washington, the rain falls for 8.5 days. Throughout December, 1.18" (30mm) of precipitation is accumulated.

How much does it snow in Grand Coulee in December?

In Grand Coulee, during December, snow falls for 10.5 days and regularly aggregates up to 3.78" (96mm) of snow.

What is the month with the shortest days in Grand Coulee?

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

How many hours of daylight does Grand Coulee have in December?

In December, the average day length in Grand Coulee is 8h and 28min.

What time are sunrise and sunset in December in Grand Coulee?

In December, on the first day of the month, sunrise is at 7:25 am and sunset at 4:05 pm. On the last day of the month, sunrise is at 7:45 am and sunset at 4:13 pm PST.

How long on average sun shines in December in Grand Coulee?

In December, the average sunshine duration in Grand Coulee, Washington, is 4.4h.

What is the UV index intensity in December in Grand Coulee?

In Grand Coulee, Washington, the average daily maximum UV index in December is 2. A UV Index of 2, and less, symbolizes a minimal hazard to health from exposure to Sun's UV rays.
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
Grand Coulee, WA

Average temperature in December - Grand Coulee, WA
  • Average high temperature in December: 31.6°F

The warmest month (with the highest average high temperature) is July (84.9°F).
The month with the lowest average high temperature is December (31.6°F).

  • Average low temperature in December: 21.4°F

The month with the highest average low temperature is August (61.3°F).
The coldest month (with the lowest average low temperature) is December (21.4°F).

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Average pressure in December
Grand Coulee, WA

Average pressure in December - Grand Coulee, WA
  • Average pressure in December: 30.15"Hg

The month with the highest atmospheric pressure is January (30.18"Hg).
The month with the lowest atmospheric pressure is August (29.91"Hg).

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Average wind speed in December
Grand Coulee, WA

Average wind speed in December - Grand Coulee, WA
  • Average wind speed in December: 5mph

The windiest month (with the highest average wind speed) is April (7mph).
The calmest month (with the lowest average wind speed) is January (4.9mph).

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Average humidity in December
Grand Coulee, WA

Average humidity in December - Grand Coulee, WA
  • Average humidity in December: 86%

The month with the highest relative humidity is January (89%).
The month with the lowest relative humidity is August (36%).

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Average rainfall in December
Grand Coulee, WA

Average rainfall in December - Grand Coulee, WA
  • Average rainfall in December: 1.18"

The wettest months (with the highest rainfall) are May and December (1.18").
The driest months (with the least rainfall) are July and August (0.2").

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Average rainfall days in December
Grand Coulee, WA

Average rainfall days in December - Grand Coulee, WA
  • Average rainfall days in December: 8.5 days

The month with the highest number of rainy days is March (12.1 days).
The month with the least rainy days is August (3.2 days).

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Average snowfall in December
Grand Coulee, WA

Average snowfall in December - Grand Coulee, WA
  • Average snowfall in December: 3.78"

The month with the highest snowfall is January (4.41").
The months with the least snowfall are May, June, July and August (0").

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Average snowfall days in December
Grand Coulee, WA

Average snowfall days in December - Grand Coulee, WA
  • Average snowfall days in December: 10.5 days

The month with the highest number of snowfall days is December (10.5 days).
The months with the least snowfall days are May, June, July and August (0 days).

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Average daylight in December /
Average sunshine in December
Grand Coulee, WA

Average daylight in December / Average sunshine in December - Grand Coulee, WA
  • Average daylight in December: 8h and 3min

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 30min).

  • Average sunshine in December: 4h and 2min

The month with the most sunshine is August (Average sunshine: 12h and 6min).
The month with the least sunshine is January (Average sunshine: 4h and 6min).

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Average sunshine days in December
Grand Coulee, WA

Average sunshine days in December - Grand Coulee, WA
  • Average sunshine days in December: 16 days

The month with the most sunshine days is August (25.8 days).
The month with the least sunshine days is March (14.7 days).

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Average UV index in December
Grand Coulee, WA

Average UV index in December - Grand Coulee, WA
  • Average UV index in December: 2

The month with the highest UV index is July (UV index 7).
The month with the lowest UV index is November (UV index 1).

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Average cloud cover in December
Grand Coulee, WA

Average cloud cover in December - Grand Coulee, WA
  • Average cloud cover in December: 52

The month with the most cloud cover is January (Cloud cover 55).
The months with the least cloud cover are July and August (Cloud cover 12).

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Average visibility in December
Grand Coulee, WA

Average visibility in December - Grand Coulee, WA
  • Average visibility in December: 4mi

The months with the highest visibility are March, April, May, June, July, August, September, October and November (6mi).
The months with the lowest visibility are January and December (4mi).

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Grand Coulee, Washington, USA

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