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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 4°C (39°F). Expect chilly days, with minimum temperatures dipping to -13°C (9°F) and highs reaching 21°C (70°F). During this month, you can anticipate about 85 mm (3.4 in) of precipitation spread over 8 days, contributing to an average humidity of 85%. Be prepared for a mix of weather!

December Temperature in Washington

In December in Washington, the average temperature is 4°C (39°F). Maximum temperatures can reach 21°C (70°F), while minimums can drop as low as -13°C (9°F). It’s advisable to pack layers to stay comfortable 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 4°C (39°F), with highs reaching up to 21°C (70°F) and lows dropping to around -13°C (9°F).
JanFebMarAprMayJunJulAugSepOctNovDec353945556472787569594539
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 85 mm (3.4 in) over the course of 8 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 85 mm (3.4 inches) of precipitation spread over approximately 8 days.
JanFebMarAprMayJunJulAugSepOctNovDec5990761051251211031321081038385
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 85%. With an average temperature of 4°C (39°F), this humidity feels like a damp chill that seeps into your bones, making traveling uncomfortable and requiring extra layers to ward off the cold and moisture.

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 85%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%86%86%84%78%79%70%59%68%80%87%85%
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 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 Washington, you can check the information here.

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 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec35710111010108753
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 Weather1°C (35°F)59 mm (2.3 inches)86%moderate
February Weather4°C (40°F)90 mm (3.6 inches)86%moderate
March Weather7°C (45°F)76 mm (3.0 inches)86%high
April Weather13°C (55°F)105 mm (4.1 inches)84%very high
May Weather18°C (65°F)125 mm (4.9 inches)78%extreme
June Weather22°C (73°F)121 mm (4.8 inches)79%very high
July Weather25°C (78°F)103 mm (4.1 inches)70%very high
August Weather24°C (75°F)132 mm (5.2 inches)59%very high
September Weather21°C (69°F)108 mm (4.3 inches)68%very high
October Weather15°C (60°F)103 mm (4.1 inches)80%high
November Weather7°C (45°F)83 mm (3.3 inches)86%moderate
December Weather4°C (39°F)85 mm (3.4 inches)85%moderate

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