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December Weather in Washington, United States

Last updated: June 24, 2025

In December, the average temperature in Washington, United States hovers around -1°C (30°F), with lows dipping to -19°C (-1°F) and highs peaking at 11°C (51°F). Expect about 70 mm (2.8 in) of precipitation spread over 10 days, and brace for high humidity levels averaging 87%.

December Temperature in Washington

In December in Washington, the average temperature is -1°C (30°F). Maximums can reach 11°C (51°F), while minimums can be as low as -19°C (-1°F). It's advisable to pack warm clothing and be prepared for cold weather during your travels.

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 -1°C (30°F), with highs reaching up to 11°C (51°F) and lows dropping to around -19°C (-1°F).
JanFebMarAprMayJunJulAugSepOctNovDec242329364557686862513830
Data source: Temperature data for Washington generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

December Precipitation in Washington

In Washington in December, the precipitation amount is 70 mm (2.8 in) over a period 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 70 mm (2.8 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec4456619083907687851146770
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Washington

In Washington in December, humidity is 87%. With an average temperature of -1°C (30°F), this humidity feels like a biting chill that penetrates through layers of clothing, making travel uncomfortable as the dampness clings to your skin, intensifying the cold and causing every gust of wind to feel even more frigid.

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 87%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec91%91%87%87%82%79%76%76%79%83%86%87%
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 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 Washington, you can visit Hourly UV Index in Washington.

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 2, which falls under the low exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec245799987532
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.
 TemperaturePrecipitationHumidityUV
January Weather-5°C (24°F)44 mm (1.7 inches)91%low
February Weather-5°C (23°F)56 mm (2.2 inches)91%moderate
March Weather-1°C (30°F)61 mm (2.4 inches)87%moderate
April Weather2°C (36°F)90 mm (3.5 inches)87%high
May Weather7°C (45°F)83 mm (3.3 inches)82%very high
June Weather14°C (57°F)90 mm (3.5 inches)79%very high
July Weather20°C (68°F)76 mm (3.0 inches)75%very high
August Weather20°C (68°F)87 mm (3.4 inches)76%very high
September Weather17°C (62°F)85 mm (3.4 inches)79%high
October Weather11°C (51°F)114 mm (4.5 inches)83%moderate
November Weather3°C (38°F)67 mm (2.6 inches)86%moderate
December Weather-1°C (30°F)70 mm (2.8 inches)87%low

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