December Weather in Washington, United States

Last updated: June 24, 2025

In December, the average temperature in Washington, United States hovers around 10°C (50°F). Be prepared for a range of temperatures, as it can dip to a chilly -5°C (23°F) and peak at a warm 26°C (79°F). With an average precipitation of 117 mm (4.6 in) spread over 10 days, expect a fair share of rainy moments. It's also worth noting the average humidity is a high 89%, adding to the climate's unique character.

December Temperature in Washington

In December in Washington, the average temperature is 10°C (50°F), with maximums reaching 26°C (79°F) and minimums dropping as low as -5°C (23°F). This diverse temperature range makes it essential for travelers to pack layers to stay comfortable throughout the day.

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

The chart illustrates December temperature patterns in Washington, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Washington, December typically has an average temperature of 10°C (50°F), with highs reaching up to 26°C (79°F) and lows dropping to around -5°C (23°F).

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

December Precipitation in Washington

In Washington in December, the total precipitation amount is 117 mm (4.6 in) recorded over a span of 10 days.

December Precipitation Trends in Washington

The chart displays monthly precipitation patterns in Washington, 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 Washington, December typically receives around 117 mm (4.6 inches) of precipitation spread over approximately 10 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 Washington

In Washington in December, humidity is 89%. With an average temperature of 10°C (50°F), this humidity feels like a dense blanket wrapping around you, making travel feel damp and chilly, and urging you to dress in layers for comfort.

December Average Humidity in Washington

This chart illustrates the average monthly humidity levels in Washington, 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 Washington is approximately 89%, 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 Washington

In Washington in December, the maximum UV index reaches 4, which corresponds to a moderate Exposure Category. With a time to burn of 30 minutes, it’s important to take precautions to protect your skin. You can find more details in the Hourly UV Index in Washington for better planning.

Maximum UV Index Levels in Washington for December

The chart shows the monthly maximum UV Index (UVI) for Washington 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 Washington typically reaches 4, which falls under the moderate exposure category.

Data source: Washington 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 Washington Compares to Other Months

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

This table compares monthly weather conditions in Washington, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	9°C (48°F)	100 mm (3.9 inches)	86%	moderate
February Weather	12°C (53°F)	117 mm (4.6 inches)	84%	high
March Weather	14°C (58°F)	87 mm (3.4 inches)	83%	very high
April Weather	18°C (65°F)	107 mm (4.2 inches)	81%	very high
May Weather	23°C (73°F)	109 mm (4.3 inches)	81%	extreme
June Weather	26°C (79°F)	97 mm (3.8 inches)	81%	extreme
July Weather	27°C (82°F)	105 mm (4.1 inches)	83%	extreme
August Weather	27°C (81°F)	125 mm (4.9 inches)	81%	very high
September Weather	25°C (77°F)	98 mm (3.9 inches)	82%	very high
October Weather	20°C (68°F)	112 mm (4.4 inches)	78%	very high
November Weather	12°C (54°F)	82 mm (3.2 inches)	86%	high
December Weather	10°C (50°F)	117 mm (4.6 inches)	89%	moderate