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May Weather in Herndon, United States

Last updated: June 24, 2025

In May, the average temperature in Herndon, United States is a pleasant 19°C (66°F), with a minimum of 2°C (35°F) and a maximum soaring up to 34°C (94°F). Expect around 131 mm (5.2 in) of precipitation spread over 13 days, while the air carries a humidity level of 78%. Be prepared for a mix of warmth and refreshing rain!

May Temperature in Herndon

In May in Herndon, the average temperature is 19°C (66°F). Maximum temperatures can reach 34°C (94°F), while minimums can drop as low as 2°C (35°F). Travelers should pack for a wide range of temperatures, from warm days to chilly nights.

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

The chart illustrates May temperature patterns in Herndon, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Herndon, May typically has an average temperature of 19°C (66°F), with highs reaching up to 34°C (94°F) and lows dropping to around 2°C (35°F).
JanFebMarAprMayJunJulAugSepOctNovDec364046566675807771614640
Data source: Temperature data for Herndon 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 Herndon

In Herndon in May, the precipitation amount is 131 mm (5.2 in) over the course of 13 days.

May Precipitation Trends in Herndon

The chart displays monthly precipitation patterns in Herndon, 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 Herndon, May typically receives around 131 mm (5.2 inches) of precipitation spread over approximately 13 days.
JanFebMarAprMayJunJulAugSepOctNovDec5997831001311101261371021058792
Data source: Precipitation data for May generated using information from the Copernicus Climate Change Service.
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May Humidity in Herndon

In Herndon in May, humidity is 78%. With an average temperature of 19°C (66°F), this humidity feels like a warm, enveloping blanket, making traveling quite uncomfortable unless you're well-prepared with lightweight, breathable clothing and frequent breaks to stay hydrated.

May Average Humidity in Herndon

This chart illustrates the average monthly humidity levels in Herndon, 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 Herndon is approximately 78%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%86%86%84%78%79%70%59%68%80%87%85%
Data source: Humidity data for May generated using information from the Copernicus Climate Change Service.

May UV Index in Herndon

In Herndon 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 Herndon.

Maximum UV Index Levels in Herndon for May

The chart shows the monthly maximum UV Index (UVI) for Herndon 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 Herndon typically reaches 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec357910101098753
Data source: Herndon 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 Herndon Compares to Other Months

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

This table compares monthly weather conditions in Herndon, showing how May’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather2°C (36°F)59 mm (2.3 inches)86%moderate
February Weather5°C (41°F)97 mm (3.8 inches)86%moderate
March Weather8°C (46°F)83 mm (3.3 inches)86%high
April Weather13°C (56°F)100 mm (3.9 inches)84%very high
May Weather19°C (66°F)131 mm (5.2 inches)78%very high
June Weather24°C (75°F)110 mm (4.3 inches)79%very high
July Weather27°C (80°F)126 mm (5.0 inches)70%very high
August Weather25°C (77°F)137 mm (5.4 inches)59%very high
September Weather22°C (71°F)102 mm (4.0 inches)68%very high
October Weather16°C (62°F)105 mm (4.1 inches)80%high
November Weather8°C (47°F)87 mm (3.4 inches)86%moderate
December Weather4°C (40°F)92 mm (3.6 inches)85%moderate

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