December weather forecast
Tri-City, OR

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Weather in December

December, the first month of the winter in Tri-City, is also a frosty month, with an average temperature varying between 32.2°F (0.1°C) and 45.7°F (7.6°C).

Temperature

The month of December, characterized by an average high of 45.7°F (7.6°C) and a low of 32.2°F (0.1°C), is recognized as the coldest.

Humidity

January, February and December, with an average relative humidity of 86%, are the most humid months.

Rainfall

The wettest months are January, February and December, with an average 1.1" (28mm) of rainfall.

Snowfall

January through March, November and December are months with snowfall. In Tri-City, Oregon, in December, during 0.5 snowfall days, 0.31" (8mm) of snow is typically accumulated. Throughout the year, in Tri-City, there are 3.5 snowfall days, and 2.2" (56mm) of snow is accumulated.

Daylight

The month with the shortest days is December, with an average of 9h and 6min of daylight.
On the first day of December, sunrise is at 7:25 am and sunset at 4:39 pm. On the last day of the month, sunrise is at 7:44 am and sunset at 4:48 pm PST.

Sunshine

With an average of 4.3h of sunshine, December has the least sunshine of the year.

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 exposure to the Sun's UV rays for average individuals.
Note: In December, the maximum UV index of 2 transforms into these recommendations:
While most people are not greatly affected by extended sun exposure, those with fair skin, babies, and children must always have protection. Solar radiation peaks around mid-day, so it's wise to limit exposure to the Sun at this time. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects. Keep in mind! Snow's reflective quality can nearly double the intensity of the Sun's UV radiation.
Updated: Aug 10, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What is the coldest month?

In Tri-City, December registers the lowest temperatures, averaging 45.7°F (7.6°C) at the peak and 32.2°F (0.1°C) at the lowest.

What are December temperatures?

During December, Tri-City experiences an average high-temperature of 45.7°F (7.6°C) and a low-temperature of 32.2°F (0.1°C). In August, the average heat index (a.k.a. 'apparent temperature', 'feels like'), which combines relative humidity and air temperature, is evaluated at 84.2°F (29°C).

What are the most humid months in Tri-City?

January, February and December, with an average relative humidity of 86%, are most humid months.

What is the average humidity in December?

In Tri-City, the average relative humidity in December is 86%.

What is the wettest month?

The months with the most rainfall are January, February and December, with an average 1.1" (28mm) of precipitation.

How many days does it rain in December?

In Tri-City, in December, during 11.4 rainfall days, 1.1" (28mm) of precipitation is typically accumulated.

How many days does it snow in December?

In Tri-City, in December, during 0.5 snowfall days, 0.31" (8mm) of snow is typically accumulated.

What is the month with the shortest days?

With an average of 9h and 6min of daylight, December has the shortest days of the year.

How many hours of daylight does Tri-City have in December?

In December, the average day length in Tri-City is 9h and 4min.

What time are sunrise and sunset in December?

In December, on the first day of the month, sunrise is at 7:25 am and sunset at 4:39 pm. On the last day of the month, sunrise is at 7:44 am and sunset at 4:48 pm PST.

What is the month with the least sunshine?

With an average of 4.3h of sunshine, December has the least sunshine of the year.

How long on average sun shines in December?

In December, the average sunshine duration is 4.3h.

What is the month with the lowest UV index?

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

How high is the UV index in December?

In Tri-City, the average daily maximum UV index in December is 2. A UV Index reading of 2, and below, represents a low health risk 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
Tri-City, OR

Average temperature in December - Tri-City, OR
  • Average high temperature in December: 45.7°F

The warmest month (with the highest average high temperature) is August (81.1°F).
The month with the lowest average high temperature is December (45.7°F).

  • Average low temperature in December: 32.2°F

The month with the highest average low temperature is August (47.7°F).
The coldest month (with the lowest average low temperature) is December (32.2°F).

Average pressure in December
Tri-City, OR

Average pressure in December - Tri-City, OR
  • Average pressure in December: 30.11"Hg

The month with the highest atmospheric pressure is January (30.12"Hg).
The month with the lowest atmospheric pressure is August (30"Hg).

Average wind speed in December
Tri-City, OR

Average wind speed in December - Tri-City, OR
  • Average wind speed in December: 3.9mph

The windiest month (with the highest average wind speed) is January (4.1mph).
The calmest month (with the lowest average wind speed) is September (3.2mph).

Average humidity in December
Tri-City, OR

Average humidity in December - Tri-City, OR
  • Average humidity in December: 86%

The months with the highest relative humidity are January, February and December (86%).
The month with the lowest relative humidity is August (69%).

Average rainfall in December
Tri-City, OR

Average rainfall in December - Tri-City, OR
  • Average rainfall in December: 1.1"

The wettest months (with the highest rainfall) are January, February and December (1.1").
The driest months (with the least rainfall) are July and August (0.16").

Average rainfall days in December
Tri-City, OR

Average rainfall days in December - Tri-City, OR
  • Average rainfall days in December: 11.4 days

The month with the highest number of rainy days is March (12.6 days).
The month with the least rainy days is August (2.4 days).

Average snowfall in December
Tri-City, OR

Average snowfall in December - Tri-City, OR
  • Average snowfall in December: 0.31"

The month with the highest snowfall is February (0.87").
The months with the least snowfall are April, May, June, July, August, September and October (0").

Average snowfall days in December
Tri-City, OR

Average snowfall days in December - Tri-City, OR
  • Average snowfall days in December: 0.5 days

The month with the highest number of snowfall days is February (1.5 days).
The months with the least snowfall days are April, May, June, July, August, September and October (0 days).

Average daylight in December /
Average sunshine in December
Tri-City, OR

Average daylight in December / Average sunshine in December - Tri-City, OR
  • Average daylight in December: 9h and 1min

The month with the longest days is June (Average daylight: 15h and 18min).
The month with the shortest days is December (Average daylight: 9h and 6min).

  • Average sunshine in December: 4h and 2min

The month with the most sunshine is August (Average sunshine: 11h and 18min).
The month with the least sunshine is December (Average sunshine: 4h and 18min).

Average sunshine days in December
Tri-City, OR

Average sunshine days in December - Tri-City, OR
  • Average sunshine days in December: 17.7 days

The month with the most sunshine days is August (26.5 days).
The month with the least sunshine days is March (16.1 days).

Average UV index in December
Tri-City, OR

Average UV index in December - Tri-City, OR
  • Average UV index in December: 2

The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).

Average cloud cover in December
Tri-City, OR

Average cloud cover in December - Tri-City, OR
  • Average cloud cover in December: 56

The month with the most cloud cover is March (Cloud cover 60).
The month with the least cloud cover is August (Cloud cover 25).

Average visibility in December
Tri-City, OR

Average visibility in December - Tri-City, OR
  • Average visibility in December: 4mi

The months with the highest visibility are July, August and September (5mi).
The months with the lowest visibility are January, February, March, April, May, June, October, November and December (4mi).

Tri-City, Oregon, USA

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