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December Weather in Tri-City, United States

Last updated: June 24, 2025

In December, the average temperature in Tri-City, United States hovers around 4°C (39°F). Expect a minimum dip to -6°C (21°F) and a pleasant maximum of 18°C (65°F). With about 140 mm (5.5 in) of precipitation spread over 15 days, you might want to keep an umbrella handy. The air is notably humid, with average humidity levels reaching 87%.

December Temperature in Tri-City

In December in Tri-City, the average temperature is 4°C (39°F), with maximums reaching 18°C (65°F) and minimums dropping to as low as -6°C (21°F). This varied temperature makes it essential for travelers to pack both warm layers and lighter clothing to accommodate shifts in the weather.

December Weather in Tri-City: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in Tri-City, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Tri-City, December typically has an average temperature of 4°C (39°F), with highs reaching up to 18°C (65°F) and lows dropping to around -6°C (21°F).
JanFebMarAprMayJunJulAugSepOctNovDec404044495562686862524539
Data source: Temperature data for Tri-City 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 Tri-City

In Tri-City in December, the total precipitation amount is 140 mm (5.5 in) over a span of 15 days.

December Precipitation Trends in Tri-City

The chart displays monthly precipitation patterns in Tri-City, 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 Tri-City, December typically receives around 140 mm (5.5 inches) of precipitation spread over approximately 15 days.
JanFebMarAprMayJunJulAugSepOctNovDec1401751241126131286167107140
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Tri-City

In Tri-City 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 Tri-City

This chart illustrates the average monthly humidity levels in Tri-City, 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 Tri-City is approximately 87%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%85%86%83%83%83%78%67%66%77%87%87%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Tri-City

In Tri-City 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 Tri-City, you can visit Hourly UV Index in Tri-City.

Maximum UV Index Levels in Tri-City for December

The chart shows the monthly maximum UV Index (UVI) for Tri-City 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 Tri-City typically reaches 2, which falls under the low exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec346810101098632
Data source: Tri-City 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 Tri-City Compares to Other Months

Weather in Tri-City varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Tri-City, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Tri-City, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather5°C (40°F)140 mm (5.5 inches)84%moderate
February Weather4°C (40°F)175 mm (6.9 inches)85%moderate
March Weather7°C (44°F)124 mm (4.9 inches)86%high
April Weather10°C (49°F)112 mm (4.4 inches)83%very high
May Weather13°C (55°F)61 mm (2.4 inches)83%very high
June Weather17°C (62°F)31 mm (1.2 inches)83%very high
July Weather20°C (68°F)2 mm (0.1 inches)78%very high
August Weather20°C (68°F)8 mm (0.3 inches)67%very high
September Weather17°C (62°F)61 mm (2.4 inches)66%very high
October Weather11°C (52°F)67 mm (2.6 inches)77%high
November Weather7°C (45°F)107 mm (4.2 inches)87%moderate
December Weather4°C (39°F)140 mm (5.5 inches)87%low

Compare Tri-City's Climate with Cities Worldwide