January Weather in Fairfax, United States

Last updated: June 24, 2025

In Fairfax, United States, the average temperature in January hovers around -9°C (16°F), with extremes ranging from a chilling -34°C (-29°F) to a mild 10°C (50°F). Expect about 26 mm (1.0 in) of precipitation over 5 days, contributing to an average humidity of 87%. Prepare for a characteristically cold and damp winter experience!

January Temperature in Fairfax

In January in Fairfax, the average temperature is -9°C (16°F), with maximums reaching 10°C (50°F) and minimums plummeting to -34°C (-29°F). Travelers should be prepared for extreme cold and dress appropriately for frigid weather conditions.

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

The chart illustrates January 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, January typically has an average temperature of -9°C (16°F), with highs reaching up to 10°C (50°F) and lows dropping to around -34°C (-29°F).

Data source: Temperature data for Fairfax generated using information from the Copernicus Climate Change Service.

January Precipitation in Fairfax

In Fairfax in January, the precipitation amount is 26 mm (1.0 in) over the course of 5 days.

January Precipitation Trends in Fairfax

The chart displays monthly precipitation patterns in Fairfax, with values for each month alongside January’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how January’s conditions compare to those of other months. In Fairfax, January typically receives around 26 mm (1.0 inches) of precipitation spread over approximately 5 days.

Data source: Precipitation data for January generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

January Humidity in Fairfax

In Fairfax in January humidity is 87%. With an average temperature of -9°C (16°F), this humidity feels like a heavy blanket of moisture that clings to your skin, making it uncomfortable for traveling and causing your breath to mist in the cold air while navigating the wintry landscape.

January Average Humidity in Fairfax

This chart illustrates the average monthly humidity levels in Fairfax, with January’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In January, average humidity in Fairfax is approximately 87%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for January generated using information from the Copernicus Climate Change Service.

January UV Index in Fairfax

In Fairfax in January, 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 January

The chart shows the monthly maximum UV Index (UVI) for Fairfax in January, 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 January, the maximum UV index in Fairfax typically reaches 3, which falls under the moderate exposure category.

Data source: Fairfax January 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 January 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 January’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 January’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-9°C (16°F)	26 mm (1.0 inches)	87%	moderate
February Weather	-9°C (16°F)	27 mm (1.1 inches)	90%	moderate
March Weather	0°C (33°F)	62 mm (2.5 inches)	85%	moderate
April Weather	6°C (43°F)	80 mm (3.1 inches)	84%	very high
May Weather	15°C (60°F)	124 mm (4.9 inches)	78%	very high
June Weather	22°C (72°F)	106 mm (4.2 inches)	80%	very high
July Weather	23°C (74°F)	123 mm (4.8 inches)	81%	very high
August Weather	21°C (71°F)	124 mm (4.9 inches)	81%	very high
September Weather	18°C (65°F)	118 mm (4.6 inches)	81%	very high
October Weather	9°C (48°F)	97 mm (3.8 inches)	84%	moderate
November Weather	1°C (34°F)	30 mm (1.2 inches)	88%	moderate
December Weather	-4°C (24°F)	40 mm (1.6 inches)	84%	low