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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). Prepare for a range that can dip as low as -16°C (4°F) and rise to a comfortable 23°C (74°F). Expect about 54 mm (2.1 in) of precipitation over approximately 6 days, all while maintaining an average humidity of 86%.

December Temperature in Washington

In December in Washington, the average temperature is 4°C (39°F), with a maximum that can reach 23°C (74°F) and a minimum that can drop to -16°C (4°F). Travelers should be prepared for a wide range of temperatures and pack accordingly.

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 23°C (74°F) and lows dropping to around -16°C (4°F).
JanFebMarAprMayJunJulAugSepOctNovDec333647556676797672594539
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 54 mm (2.1 in) over the course of 6 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 54 mm (2.1 inches) of precipitation spread over approximately 6 days.
JanFebMarAprMayJunJulAugSepOctNovDec758012612615289100145551086955
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 86%. With an average temperature of 4°C (39°F), this humidity feels like a chilly mist enveloping you, making it essential to bundle up while exploring, as each breath comes with a damp chill that can be quite refreshing yet starkly invigorating for travelers.

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 86%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%80%80%80%82%83%81%80%76%76%85%86%
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.
JanFebMarAprMayJunJulAugSepOctNovDec3569101111109753
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 Weather0°C (33°F)75 mm (2.9 inches)82%moderate
February Weather2°C (36°F)80 mm (3.1 inches)80%moderate
March Weather8°C (47°F)126 mm (5.0 inches)80%high
April Weather13°C (55°F)126 mm (5.0 inches)80%very high
May Weather19°C (66°F)152 mm (6.0 inches)82%very high
June Weather24°C (76°F)89 mm (3.5 inches)83%extreme
July Weather26°C (79°F)100 mm (3.9 inches)81%extreme
August Weather24°C (76°F)145 mm (5.7 inches)80%very high
September Weather22°C (72°F)55 mm (2.2 inches)76%very high
October Weather15°C (59°F)108 mm (4.2 inches)76%high
November Weather7°C (45°F)69 mm (2.7 inches)85%moderate
December Weather4°C (39°F)54 mm (2.1 inches)86%moderate

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