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May Weather in Fairfax, United States

Last updated: June 24, 2025

In May, the average temperature in Fairfax, United States hovers around 18°C (65°F), although it can fluctuate between a brisk 2°C (37°F) and a sweltering 37°C (100°F). During this month, expect about 157 mm (6.2 in) of precipitation spread over 14 days, contributing to an average humidity of 78%. Stay prepared for varying weather as you explore this charming destination!

May Temperature in Fairfax

In May in Fairfax, the average temperature is 18°C (65°F). The maximum can reach 37°C (100°F), and the minimum can be as low as 2°C (37°F). Travelers should be prepared for a wide range of temperatures, so layering clothing is advisable.

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 18°C (65°F), with highs reaching up to 37°C (100°F) and lows dropping to around 2°C (37°F).
JanFebMarAprMayJunJulAugSepOctNovDec282944526577797571554234
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 precipitation amount is 157 mm (6.2 in) spread over a duration of 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 157 mm (6.2 inches) of precipitation spread over approximately 14 days.
JanFebMarAprMayJunJulAugSepOctNovDec36329284157119112120851293732
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 78%. With an average temperature of 18°C (65°F), this humidity feels like a warm, enveloping blanket, making travel quite muggy and potentially uncomfortable, as it can leave you feeling sticky and fatigued more quickly than usual.

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 78%, 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 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.
JanFebMarAprMayJunJulAugSepOctNovDec356910111098643
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 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

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