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December Weather in Washington, United States

Last updated: June 24, 2025

In Washington, United States, the average temperature in December hovers around -1°C (30°F), with lows potentially plunging to -21°C (-5°F) and highs reaching up to 15°C (59°F). This month typically experiences 130 mm (5.1 in) of precipitation spread over 11 days, contributing to an average humidity level of 84%. Stay prepared for a chilly and damp backdrop!

December Temperature in Washington

In December in Washington, the average temperature is -1°C (30°F), with a maximum that can reach 15°C (59°F) and a minimum that can drop as low as -21°C (-5°F). Be prepared for a wide range of temperatures if you're planning to travel 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 -1°C (30°F), with highs reaching up to 15°C (59°F) and lows dropping to around -21°C (-5°F).
JanFebMarAprMayJunJulAugSepOctNovDec262834465766727063523930
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 total precipitation amount is 130 mm (5.1 in) occurring over 11 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 130 mm (5.1 inches) of precipitation spread over approximately 11 days.
JanFebMarAprMayJunJulAugSepOctNovDec8610490157121109182143129175106130
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 84%. With an average temperature of -1°C (30°F), this humidity feels like a sharp chill that seeps into your bones, making travel uncomfortable as the wetness in the air intensifies the cold, leaving you yearning for warmth and shelter.

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 84%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec90%88%86%84%76%72%67%64%72%81%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 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.
JanFebMarAprMayJunJulAugSepOctNovDec35681010998642
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-4°C (26°F)86 mm (3.4 inches)89%moderate
February Weather-2°C (29°F)104 mm (4.1 inches)88%moderate
March Weather1°C (34°F)90 mm (3.6 inches)86%high
April Weather8°C (46°F)157 mm (6.2 inches)84%very high
May Weather14°C (57°F)121 mm (4.8 inches)76%very high
June Weather19°C (67°F)109 mm (4.3 inches)72%very high
July Weather22°C (72°F)182 mm (7.1 inches)66%very high
August Weather21°C (70°F)143 mm (5.6 inches)64%very high
September Weather17°C (63°F)129 mm (5.1 inches)72%very high
October Weather11°C (53°F)174 mm (6.9 inches)81%high
November Weather4°C (39°F)106 mm (4.2 inches)87%moderate
December Weather-1°C (30°F)130 mm (5.1 inches)84%low

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