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May Weather in Fairfax, United States

Last updated: June 24, 2025

In Fairfax, United States, the average temperature in May is a pleasant 20°C (69°F). However, be prepared for fluctuations, as temperatures can dip to a chilly 4°C (40°F) or rise to a sweltering 34°C (94°F). With 160 mm (6.3 in) of precipitation spread over 14 days, expect some rain during your visit. Additionally, the average humidity is a notable 83%, adding to the region's unique charm.

May Temperature in Fairfax

In May in Fairfax, the average temperature is 20°C (69°F). Maximums can reach 34°C (94°F), and minimums can be as low as 4°C (40°F). This makes it a great time to explore Fairfax, as you'll experience mild weather with the potential for warm days and cooler nights.

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

The chart illustrates May 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, May typically has an average temperature of 20°C (69°F), with highs reaching up to 34°C (94°F) and lows dropping to around 4°C (40°F).
JanFebMarAprMayJunJulAugSepOctNovDec373952586979828075614942
Data source: Temperature data for Fairfax 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.

May Precipitation in Fairfax

In Fairfax in May, the total precipitation amount is 160 mm (6.3 in) spread over 14 days.

May Precipitation Trends in Fairfax

The chart displays monthly precipitation patterns in Fairfax, with values for each month alongside May’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how May’s conditions compare to those of other months. In Fairfax, May typically receives around 160 mm (6.3 inches) of precipitation spread over approximately 14 days.
JanFebMarAprMayJunJulAugSepOctNovDec57449710416010281103881213435
Data source: Precipitation data for May generated using information from the Copernicus Climate Change Service.
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May Humidity in Fairfax

In Fairfax in May, humidity is 83%. With an average temperature of 20°C (69°F), this humidity feels like a warm embrace, making every step slightly more laborious and the air thick with moisture, which can be quite stifling for traveling.

May Average Humidity in Fairfax

This chart illustrates the average monthly humidity levels in Fairfax, with May’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In May, average humidity in Fairfax is approximately 83%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec77%76%71%74%83%83%81%73%67%72%82%85%
Data source: Humidity data for May generated using information from the Copernicus Climate Change Service.

May UV Index in Fairfax

In Fairfax in May, the maximum UV index reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more detailed information, you can check the Hourly UV Index in Fairfax.

Maximum UV Index Levels in Fairfax for May

The chart shows the monthly maximum UV Index (UVI) for Fairfax in May, 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 May, the maximum UV index in Fairfax typically reaches 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec36710101111109753
Data source: Fairfax May 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 May 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 May’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 May’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather3°C (38°F)57 mm (2.3 inches)77%moderate
February Weather4°C (39°F)43 mm (1.7 inches)76%high
March Weather11°C (52°F)97 mm (3.8 inches)71%high
April Weather15°C (59°F)104 mm (4.1 inches)73%very high
May Weather20°C (69°F)160 mm (6.3 inches)83%very high
June Weather26°C (79°F)101 mm (4.0 inches)83%extreme
July Weather28°C (82°F)80 mm (3.2 inches)81%extreme
August Weather27°C (80°F)103 mm (4.1 inches)73%very high
September Weather24°C (76°F)88 mm (3.4 inches)67%very high
October Weather16°C (61°F)121 mm (4.8 inches)72%high
November Weather9°C (49°F)34 mm (1.3 inches)82%moderate
December Weather6°C (43°F)35 mm (1.4 inches)85%moderate

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