December Weather in Rockville, United States

Last updated: June 24, 2025

In Rockville, United States, the average temperature in December hovers around -6°C (22°F), with a minimum dipping to -27°C (-17°F) and a maximum reaching up to 10°C (50°F). Expect some moisture, with precipitation totaling 45 mm (1.8 in) over the course of 6 days. The air will feel quite humid, with an average humidity level of 84%.

December Temperature in Rockville

In December in Rockville, the average temperature is -6°C (22°F), with maximums reaching 10°C (50°F) and minimums dropping as low as -27°C (-17°F). Travelers should be prepared for cold weather conditions and dress accordingly for a comfortable visit.

December Weather in Rockville: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in Rockville, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Rockville, December typically has an average temperature of -6°C (22°F), with highs reaching up to 10°C (50°F) and lows dropping to around -27°C (-17°F).

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

December Precipitation in Rockville

In Rockville in December, the precipitation amount is 45 mm (1.8 in) over the course of 6 days.

December Precipitation Trends in Rockville

The chart displays monthly precipitation patterns in Rockville, 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 Rockville, December typically receives around 45 mm (1.8 inches) of precipitation spread over approximately 6 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 Rockville

In Rockville in December humidity is 84%. With an average temperature of -6°C (22°F), this humidity feels like an unpleasant chill that seeps into your bones, making travel feel much more uncomfortable and harsh than the temperature alone suggests.

December Average Humidity in Rockville

This chart illustrates the average monthly humidity levels in Rockville, 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 Rockville is approximately 84%, 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 Rockville

In Rockville in December, the maximum UV index is 2, which corresponds to a low exposure category. With this level of UV radiation, the time to burn is approximately 45 minutes. To learn more about the hourly UV index in Rockville, you can visit Hourly UV Index in Rockville.

Maximum UV Index Levels in Rockville for December

The chart shows the monthly maximum UV Index (UVI) for Rockville 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 Rockville typically reaches 2, which falls under the low exposure category.

Data source: Rockville 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 Rockville Compares to Other Months

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

This table compares monthly weather conditions in Rockville, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-10°C (15°F)	19 mm (0.8 inches)	87%	low
February Weather	-10°C (15°F)	24 mm (1.0 inches)	90%	moderate
March Weather	0°C (31°F)	50 mm (2.0 inches)	85%	moderate
April Weather	5°C (42°F)	81 mm (3.2 inches)	84%	high
May Weather	14°C (58°F)	95 mm (3.7 inches)	78%	very high
June Weather	21°C (71°F)	69 mm (2.7 inches)	80%	very high
July Weather	23°C (74°F)	98 mm (3.9 inches)	81%	very high
August Weather	21°C (70°F)	143 mm (5.6 inches)	81%	very high
September Weather	17°C (63°F)	115 mm (4.5 inches)	81%	high
October Weather	8°C (47°F)	103 mm (4.1 inches)	84%	moderate
November Weather	0°C (32°F)	29 mm (1.2 inches)	88%	moderate
December Weather	-6°C (22°F)	45 mm (1.8 inches)	84%	low