nomadseason

December Weather in Fairfax, United States

Last updated: June 24, 2025

In December, the average temperature in Fairfax, United States hovers around 1°C (35°F). Expect a chill, with minimums plunging to -22°C (-7°F), while occasionally warming up to a maximum of 23°C (73°F). During this month, precipitation is moderate, averaging 32 mm (1.3 in) over just 3 days, paired with a relatively high average humidity of 83%.

December Temperature in Fairfax

In December in Fairfax, the average temperature is 1°C (35°F). The maximum can reach 23°C (73°F) and the minimum can drop to as low as -22°C (-7°F). Be prepared for a wide range of temperatures if you plan to travel during this time.

December Weather in Fairfax: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in Fairfax, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Fairfax, December typically has an average temperature of 1°C (35°F), with highs reaching up to 23°C (73°F) and lows dropping to around -22°C (-7°F).
JanFebMarAprMayJunJulAugSepOctNovDec282944526577797571554234
Data source: Temperature data for Fairfax 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 Fairfax

In Fairfax in December, the total precipitation amount is 32 mm (1.3 in) over a span of 3 days.

December Precipitation Trends in Fairfax

The chart displays monthly precipitation patterns in Fairfax, 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 Fairfax, December typically receives around 32 mm (1.3 inches) of precipitation spread over approximately 3 days.
JanFebMarAprMayJunJulAugSepOctNovDec36329284157119112120851293732
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
Choose your preferred precipitation unit

December Humidity in Fairfax

In Fairfax in December humidity is 83%. With an average temperature of 1°C (35°F), this humidity feels like a damp chill enveloping you, making travel uncomfortable as you contend with the biting cold paired with the heavy moisture in the air.

December Average Humidity in Fairfax

This chart illustrates the average monthly humidity levels in Fairfax, 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 Fairfax is approximately 83%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec76%80%73%75%78%82%83%81%75%75%82%83%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Fairfax

In Fairfax 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 Fairfax, you can check the information here.

Maximum UV Index Levels in Fairfax for December

The chart shows the monthly maximum UV Index (UVI) for Fairfax 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 Fairfax typically reaches 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec356910111098643
Data source: Fairfax 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 Fairfax Compares to Other Months

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

This table compares monthly weather conditions in Fairfax, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-2°C (28°F)36 mm (1.4 inches)76%moderate
February Weather-2°C (29°F)32 mm (1.2 inches)80%moderate
March Weather7°C (44°F)92 mm (3.6 inches)73%high
April Weather11°C (53°F)84 mm (3.3 inches)74%very high
May Weather18°C (65°F)157 mm (6.2 inches)78%very high
June Weather25°C (77°F)119 mm (4.7 inches)82%extreme
July Weather26°C (79°F)112 mm (4.4 inches)83%very high
August Weather24°C (76°F)120 mm (4.7 inches)80%very high
September Weather22°C (71°F)85 mm (3.3 inches)75%very high
October Weather13°C (55°F)129 mm (5.1 inches)75%high
November Weather6°C (42°F)37 mm (1.5 inches)82%moderate
December Weather1°C (35°F)32 mm (1.3 inches)83%moderate

Compare Fairfax's Climate with Cities Worldwide