nomadseason

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). Be prepared for a temperature range that can plunge to a minimum of -17°C (2°F) and peak at 21°C (69°F). With an average precipitation of 104 mm (4.1 in) spread over 10 days, it's wise to pack your umbrella. The air is quite humidity-rich, maintaining an average of 87%, making for a chilly yet captivating atmosphere.

December Temperature in Washington

In December in Washington, the average temperature is 4°C (39°F). Maximums can reach 21°C (69°F), while minimums can drop as low as -17°C (2°F). Be prepared for a wide range of temperatures when traveling to Washington during this time.

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 (69°F) and lows dropping to around -17°C (2°F).
JanFebMarAprMayJunJulAugSepOctNovDec333746556776797672604439
Data source: Temperature data for Washington generated using information from the Copernicus Climate Change Service.
Choose your preferred temperature unit
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 104 mm (4.1 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 104 mm (4.1 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec9411413912313311889917197102104
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
Choose your preferred precipitation unit

December Humidity in Washington

In Washington in December, humidity is 87%. With an average temperature of 4°C (39°F), this humidity feels like a damp chill that seeps into your bones, making travel uncomfortable and gritty, as the air hangs heavy and clings to your skin.

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.
JanFebMarAprMayJunJulAugSepOctNovDec87%85%86%84%79%82%79%70%69%76%88%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 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.
JanFebMarAprMayJunJulAugSepOctNovDec357910111098643
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 (33°F)93 mm (3.7 inches)87%moderate
February Weather3°C (37°F)114 mm (4.5 inches)85%moderate
March Weather8°C (47°F)139 mm (5.5 inches)86%high
April Weather13°C (55°F)123 mm (4.8 inches)84%very high
May Weather20°C (67°F)133 mm (5.2 inches)79%very high
June Weather24°C (76°F)118 mm (4.6 inches)82%extreme
July Weather26°C (79°F)89 mm (3.5 inches)79%very high
August Weather24°C (76°F)91 mm (3.6 inches)70%very high
September Weather22°C (72°F)71 mm (2.8 inches)69%very high
October Weather16°C (60°F)97 mm (3.8 inches)76%high
November Weather7°C (44°F)102 mm (4.0 inches)88%moderate
December Weather4°C (39°F)104 mm (4.1 inches)87%moderate

Compare Washington's Climate with Cities Worldwide