January Weather in Fairfax, United States

Last updated: June 24, 2025

In January, the average temperature in Fairfax, United States hovers around 3°C (38°F). Temperatures can vary dramatically, with a minimum of -17°C (2°F) and a maximum soaring to 23°C (74°F). You can expect 57 mm (2.3 in) of precipitation over about 5 days, contributing to an average humidity of 77%—perfect for those cool, crisp days!

January Temperature in Fairfax

In January in Fairfax, the average temperature is 3°C (38°F). Maximum temperatures can reach 23°C (74°F), while the minimums can drop as low as -17°C (2°F). Pack accordingly for a range of weather conditions if you're traveling during this time.

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 3°C (38°F), with highs reaching up to 23°C (74°F) and lows dropping to around -17°C (2°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 total precipitation amount is 57 mm (2.3 in) accumulated over 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 57 mm (2.3 inches) of precipitation spread over approximately 5 days.

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

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

January Humidity in Fairfax

In Fairfax in January humidity is 77%. With an average temperature of 3°C (38°F), this humidity feels like a damp chill enveloping you, making any outdoor adventure feel more intense as you navigate the biting cold mixed with the heavy air.

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 77%, 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	3°C (38°F)	57 mm (2.3 inches)	77%	moderate
February Weather	4°C (39°F)	43 mm (1.7 inches)	76%	high
March Weather	11°C (52°F)	97 mm (3.8 inches)	71%	high
April Weather	15°C (59°F)	104 mm (4.1 inches)	73%	very high
May Weather	20°C (69°F)	160 mm (6.3 inches)	83%	very high
June Weather	26°C (79°F)	101 mm (4.0 inches)	83%	extreme
July Weather	28°C (82°F)	80 mm (3.2 inches)	81%	extreme
August Weather	27°C (80°F)	103 mm (4.1 inches)	73%	very high
September Weather	24°C (76°F)	88 mm (3.4 inches)	67%	very high
October Weather	16°C (61°F)	121 mm (4.8 inches)	72%	high
November Weather	9°C (49°F)	34 mm (1.3 inches)	82%	moderate
December Weather	6°C (43°F)	35 mm (1.4 inches)	85%	moderate