December weather forecast
Grass Valley, CA

Share

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.
[Resources]

Frequently asked questions

What month is the coldest in Grass Valley?

December, noted for its average high-temperature of 51.3°F (10.7°C) and an average low-temperature of 37.2°F (2.9°C), is considered the coldest month in Grass Valley, California.

What is the usual temperature for Grass Valley in December?

The high-temperature, in December, in Grass Valley, records 51.3°F (10.7°C), while the low-temperature is 37.2°F (2.9°C). In September, the average heat index (a.k.a. 'felt air temperature', 'feels like'), which takes the relative humidity and factors it into the air temperature reading, is estimated at 82.4°F (28°C).

What is the average humidity in December in Grass Valley?

In December, the average relative humidity in Grass Valley is 68%.

How much does it rain in Grass Valley in December?

In Grass Valley, in December, it is raining for 10.7 days, with typically 5.35" (136mm) of accumulated precipitation.

How many days does it snow in December in Grass Valley?

In Grass Valley, in December, snow falls for 0.5 days, with typically accumulated 0.71" (18mm) of snow.

What is the month with the shortest days in Grass Valley?

December has the shortest days of the year, with an average of 9h and 30min of daylight.

How many hours of daylight does Grass Valley have in December?

In December, the average day length in Grass Valley is 9h and 28min.

What time are sunrise and sunset in December in Grass Valley?

In December, on the first day of the month, sunrise is at 7:05 am and sunset at 4:41 pm. On the last day of the month, in Grass Valley, sunrise is at 7:23 am and sunset at 4:51 pm PST.

How long on average sun shines in December in Grass Valley?

In Grass Valley, California, the average sunshine duration in December is 5.8h.

How high is the UV index in December in Grass Valley?

In December, the average daily maximum UV index in Grass Valley is 3. A UV Index value of 3 to 5 symbolizes a moderate health threat 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
Grass Valley, CA

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).

[Resources]

Average pressure in December
Grass Valley, CA

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).

[Resources]

Average wind speed in December
Grass Valley, CA

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).

[Resources]

Average humidity in December
Grass Valley, CA

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%).

[Resources]

Average rainfall in December
Grass Valley, CA

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").

[Resources]

Average rainfall days in December
Grass Valley, CA

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).

[Resources]

Average snowfall in December
Grass Valley, CA

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").

[Resources]

Average snowfall days in December
Grass Valley, CA

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).

[Resources]

Average daylight in December /
Average sunshine in December
Grass Valley, CA

Average daylight in December / Average sunshine in December - Grass Valley, CA
  • Average daylight in December: 9h and 3min

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 5min

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).

[Resources]

Average sunshine days in December
Grass Valley, CA

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).

[Resources]

Average UV index in December
Grass Valley, CA

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).

[Resources]

Average cloud cover in December
Grass Valley, CA

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).

[Resources]

Average visibility in December
Grass Valley, CA

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).

[Resources]

Grass Valley, California, USA

Weather forecast for your location

1. Click Locate me button
2. Allow the app to use your location