Contents
- Weather in December
- Frequently asked questions
- Average temperature in December
- Average pressure in December
- Average wind speed in December
- Average humidity in December
- Average rainfall in December
- Average rainfall days in December
- Average snowfall in December
- Average snowfall days in December
- Average daylight in December
- Average sunshine in December
- Average sunshine days in December
- Average UV index in December
- Average cloud cover in December
- Average visibility in December
Weather in December
Temperature
December is the month that records the lowest temperatures, with averages ranging from a high of 34.5°F (1.4°C) to a low of 24.3°F (-4.3°C).Humidity
The average relative humidity in December is 81%.Rainfall
The wettest months are January and December, with an average 0.87" (22mm) of rainfall.Snowfall
January through April, September, November and December are months with snowfall. December is the month with the most snowfall. Snow falls for 6.5 days and accumulates 3.43" (87mm) of snow.Daylight
December has the shortest days of the year, with an average of 8h and 36min of daylight.On the first day of December in Mattawa, sunrise is at 7:24 am and sunset at 4:13 pm. On the last day of the month, sunrise is at 7:44 am and sunset at 4:21 pm PST.
Sunshine
In December, the average sunshine is 5.1h.UV index
The months with the lowest UV index are January, February, November and December, with an average maximum UV index of 2. A UV Index estimate of 2, and below, represents a minimal health vulnerability from exposure to the Sun's UV radiation for average individuals.Note: In December, a daily maximum UV index of 2 leads to the following instructions:
Long-term sun exposure is typically not a concern for most. However, those with sensitive skin, infants, and children must always have protection. It's crucial to reduce time in the direct Sun around mid-day due to the intense solar radiation. Outfit yourself in sun-safe attire, like long sleeves, pants, a hat, and UV-blocking sunglasses. Consider carefully! The reflective quality of snow can almost double the intensity of the Sun's UV radiation.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the coldest time of year in Mattawa?
How cold is December?
What is the average humidity in December?
What is the wettest month?
How many days does it rain in December?
When does it snow the most?
How many days does it snow in December?
What is the month with the shortest days?
What is the average length of the day in December?
When is the sunrise / sunset in December?
How long on average sun shines in December?
When is the lowest UV index in Mattawa?
How high is the UV index in December in Mattawa?
Average temperature in December
Mattawa, WA
- Average high temperature in December: 34.5°F
The warmest months (with the highest average high temperature) are July and August (88.3°F).
The month with the lowest average high temperature is December (34.5°F).
- Average low temperature in December: 24.3°F
The month with the highest average low temperature is August (61.5°F).
The coldest month (with the lowest average low temperature) is December (24.3°F).
Average pressure in December
Mattawa, WA
- Average pressure in December: 30.14"Hg
The month with the highest atmospheric pressure is January (30.17"Hg).
The month with the lowest atmospheric pressure is August (29.91"Hg).
Average wind speed in December
Mattawa, WA
- Average wind speed in December: 4.7mph
The windiest month (with the highest average wind speed) is April (7.6mph).
The calmest month (with the lowest average wind speed) is December (4.7mph).
Average humidity in December
Mattawa, WA
- Average humidity in December: 81%
The month with the highest relative humidity is January (83%).
The month with the lowest relative humidity is July (37%).
Average rainfall in December
Mattawa, WA
- Average rainfall in December: 0.87"
The wettest months (with the highest rainfall) are January and December (0.87").
The driest month (with the least rainfall) is August (0.2").
Average rainfall days in December
Mattawa, WA
- Average rainfall days in December: 7.9 days
The month with the highest number of rainy days is March (10.6 days).
The month with the least rainy days is August (3.5 days).
Average snowfall in December
Mattawa, WA
- Average snowfall in December: 3.43"
The month with the highest snowfall is December (3.43").
The months with the least snowfall are May, June, July, August and October (0").
Average snowfall days in December
Mattawa, WA
- Average snowfall days in December: 6.5 days
The month with the highest number of snowfall days is December (6.5 days).
The months with the least snowfall days are May, June, July and August (0 days).
Average daylight in December /
Average sunshine in December
Mattawa, WA
- Average daylight in December: 8h and 4min
The month with the longest days is June (Average daylight: 15h and 48min).
The month with the shortest days is December (Average daylight: 8h and 36min).
- Average sunshine in December: 5h and 1min
The months with the most sunshine are July and August (Average sunshine: 12h and 0min).
The month with the least sunshine is January (Average sunshine: 4h and 54min).
Average sunshine days in December
Mattawa, WA
- Average sunshine days in December: 18.1 days
The months with the most sunshine days are July and August (25.8 days).
The month with the least sunshine days is February (16 days).
Average UV index in December
Mattawa, WA
- Average UV index in December: 2
The month with the highest UV index is July (UV index 7).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in December
Mattawa, WA
- Average cloud cover in December: 45
The month with the most cloud cover is January (Cloud cover 47).
The months with the least cloud cover are July and August (Cloud cover 10).
Average visibility in December
Mattawa, WA
- Average visibility in December: 5mi
The months with the highest visibility are February, March, April, May, June, July, August, September, October and November (6mi).
The months with the lowest visibility are January and December (5mi).
Mattawa, Washington, USA
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