December Weather in Grass Valley, United States

Last updated: June 24, 2025

In December, the average temperature in Grass Valley, United States hovers around 7°C (44°F), with temperatures ranging from a brisk -3°C (28°F) to a pleasant 22°C (72°F). This month sees 215 mm (8.4 in) of rain over approximately 11 days, contributing to an average humidity of 83%. Prepare for a mix of cool breezes and damp days!

December Temperature in Grass Valley

In December in Grass Valley, the average temperature is 7°C (44°F). Maximums can reach 22°C (72°F), while minimums can be as low as -3°C (28°F). Overall, this month offers a diverse range of temperatures, making it a unique time to explore Grass Valley.

December Weather in Grass Valley: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in Grass Valley, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Grass Valley, December typically has an average temperature of 7°C (44°F), with highs reaching up to 22°C (72°F) and lows dropping to around -3°C (28°F).

Data source: Temperature data for Grass Valley generated using information from the Copernicus Climate Change Service.

December Precipitation in Grass Valley

In Grass Valley in December, the precipitation amount is 215 mm (8.4 in) over the course of 11 days.

December Precipitation Trends in Grass Valley

The chart displays monthly precipitation patterns in Grass Valley, with values for each month alongside December’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how December’s conditions compare to those of other months. In Grass Valley, December typically receives around 215 mm (8.4 inches) of precipitation spread over approximately 11 days.

Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

December Humidity in Grass Valley

In Grass Valley in December, humidity is 83%. With an average temperature of 7°C (44°F), this humidity feels like a damp chill that seeps into your bones, making exploring outdoors somewhat uncomfortable and requiring extra layers to stay warm and dry.

December Average Humidity in Grass Valley

This chart illustrates the average monthly humidity levels in Grass Valley, with December’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In December, average humidity in Grass Valley is approximately 83%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Grass Valley

In Grass Valley in December, the maximum UV index is 3, which corresponds to a moderate Exposure Category. The time to burn is approximately 30 minutes. For more details on the hourly UV index in Grass Valley, you can check the information here.

Maximum UV Index Levels in Grass Valley for December

The chart shows the monthly maximum UV Index (UVI) for Grass Valley in December, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In December, the maximum UV index in Grass Valley typically reaches 3, which falls under the moderate exposure category.

Data source: Grass Valley December UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

Extreme (11+): Avoid the sun, stay in shade.
Very High (8-10): Limit sun exposure.
High (6-7): Use SPF 30+ and protective clothing.
Moderate (3-5): Midday shade recommended.
Low (0-2): No protection needed.

How December Weather in Grass Valley Compares to Other Months

Weather in Grass Valley varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Grass Valley, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Grass Valley, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	7°C (45°F)	269 mm (10.6 inches)	84%	moderate
February Weather	8°C (46°F)	279 mm (11.0 inches)	84%	moderate
March Weather	9°C (48°F)	267 mm (10.5 inches)	83%	high
April Weather	13°C (55°F)	129 mm (5.1 inches)	81%	very high
May Weather	17°C (62°F)	76 mm (3.0 inches)	74%	very high
June Weather	22°C (72°F)	13 mm (0.5 inches)	64%	extreme
July Weather	26°C (79°F)	1 mm (0.0 inches)	44%	extreme
August Weather	25°C (77°F)	2 mm (0.1 inches)	36%	very high
September Weather	21°C (70°F)	23 mm (0.9 inches)	44%	very high
October Weather	15°C (60°F)	78 mm (3.1 inches)	65%	high
November Weather	10°C (51°F)	157 mm (6.2 inches)	84%	moderate
December Weather	7°C (44°F)	215 mm (8.4 inches)	83%	moderate