December weather forecastGrass Valley, CA
December
Weather in December
The first month of the winter, December, is also a fresh month in Grass Valley, California, with an average temperature fluctuating between 37.2°F (2.9°C) and 51.3°F (10.7°C).Temperature
December is the coldest month, with the temperature often reaching an average high of 51.3°F (10.7°C) and an average low of 37.2°F (2.9°C).Humidity
In Grass Valley, the average relative humidity in December is 68%.Rainfall
In Grass Valley, during December, the rain falls for 10.7 days and regularly aggregates up to 5.35" (136mm) of precipitation. Throughout the year, there are 82 rainfall days, and 33.11" (841mm) of precipitation is accumulated.Snowfall
January through May, November and December are months with snowfall in Grass Valley, California. In December, in Grass Valley, it is snowing for 0.5 days. Throughout December, 0.71" (18mm) of snow is accumulated. Throughout the year, in Grass Valley, there are 6.8 snowfall days, and 14.41" (366mm) of snow is accumulated.Daylight
The month with the shortest days in Grass Valley is December, with an average of 9h and 30min of daylight.On the first day of December in Grass Valley, sunrise is at 7:05 am and sunset at 4:41 pm. On the last day of the month, sunrise is at 7:23 am and sunset at 4:51 pm PST.
Sunshine
In December, the average sunshine in Grass Valley is 5.8h.UV index
The average daily maximum UV index in December is 3. A UV Index value of 3 to 5 symbolizes a medium health hazard from exposure to the Sun's UV rays for average individuals.Note: In December, a daily UV index of 3 turns into the following recommendations:
Be mindful. Individuals with a lighter skin tone may suffer burns in less than 30 minutes. Avoiding the Sun's peak radiation during midday hours is essential for health and safety. For holistic sun protection encompassing the eyes, ears, face, and neck, a wide-brim hat is key. Take careful note! The UV radiation of the Sun can be nearly doubled by snow reflection.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Grass Valley, CA
- Average high temperature in December: 51.3°F
The warmest month (with the highest average high temperature) is July (90.1°F).
The month with the lowest average high temperature is December (51.3°F).
- Average low temperature in December: 37.2°F
The month with the highest average low temperature is July (60.1°F).
The coldest month (with the lowest average low temperature) is December (37.2°F).
Average pressure in December
Grass Valley, CA
- 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 June (29.9"Hg).
Average wind speed in December
Grass Valley, CA
- Average wind speed in December: 5.3mph
The windiest month (with the highest average wind speed) is February (6mph).
The calmest month (with the lowest average wind speed) is August (4.8mph).
Average humidity in December
Grass Valley, CA
- Average humidity in December: 68%
The month with the highest relative humidity is March (75%).
The month with the lowest relative humidity is July (37%).
Average rainfall in December
Grass Valley, CA
- Average rainfall in December: 5.35"
The wettest month (with the highest rainfall) is March (6.57").
The driest months (with the least rainfall) are July and August (0.04").
Average rainfall days in December
Grass Valley, CA
- Average rainfall days in December: 10.7 days
The month with the highest number of rainy days is March (15.1 days).
The month with the least rainy days is July (1.1 days).
Average snowfall in December
Grass Valley, CA
- Average snowfall in December: 0.71"
The month with the highest snowfall is February (6.42").
The months with the least snowfall are June, July, August, September and October (0").
Average snowfall days in December
Grass Valley, CA
- Average snowfall days in December: 0.5 days
The month with the highest number of snowfall days is March (2.4 days).
The months with the least snowfall days are June, July, August, September and October (0 days).
Average daylight in December /
Average sunshine in December
Grass Valley, CA
- Average daylight in December: 9h and 30min
The month with the longest days is June (Average daylight: 14h and 54min).
The month with the shortest days is December (Average daylight: 9h and 30min).
- Average sunshine in December: 5h and 48min
The month with the most sunshine is July (Average sunshine: 12h and 12min).
The month with the least sunshine is January (Average sunshine: 5h and 42min).
Average sunshine days in December
Grass Valley, CA
- Average sunshine days in December: 19.1 days
The month with the most sunshine days is July (29.8 days).
The month with the least sunshine days is March (14.8 days).
Average UV index in December
Grass Valley, CA
- Average UV index in December: 3
The month with the highest UV index is July (UV index 7).
The month with the lowest UV index is November (UV index 2).
Average cloud cover in December
Grass Valley, CA
- Average cloud cover in December: 35
The month with the most cloud cover is March (Cloud cover 41).
The month with the least cloud cover is July (Cloud cover 4).
Average visibility in December
Grass Valley, CA
- 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).
