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May Weather in Helena, United States

Last updated: June 24, 2025

In May, the average temperature in Helena, United States hovers around 20°C (69°F). Be prepared for a wide range of temperatures, with lows of 4°C (40°F) and highs reaching 36°C (97°F). This month also sees 143 mm (5.6 in) of precipitation spread over 13 days, contributing to an average humidity level of 82%.

May Temperature in Helena

In May in Helena, the average temperature is 20°C (69°F). Maximums can reach 36°C (97°F) while minimums can drop to as low as 4°C (40°F). This variety in temperatures makes it essential for travelers to pack both light clothing for the warmer days and layers for cooler evenings.

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

The chart illustrates May temperature patterns in Helena, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Helena, May typically has an average temperature of 20°C (69°F), with highs reaching up to 36°C (97°F) and lows dropping to around 4°C (40°F).
JanFebMarAprMayJunJulAugSepOctNovDec373852586979838075604841
Data source: Temperature data for Helena 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 Helena

In Helena in May, the precipitation amount is 143 mm (5.6 in) over a span of 13 days.

May Precipitation Trends in Helena

The chart displays monthly precipitation patterns in Helena, 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 Helena, May typically receives around 143 mm (5.6 inches) of precipitation spread over approximately 13 days.
JanFebMarAprMayJunJulAugSepOctNovDec35247782143112456959862129
Data source: Precipitation data for May generated using information from the Copernicus Climate Change Service.
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May Humidity in Helena

In Helena in May humidity is 82%. With an average temperature of 20°C (69°F), this humidity feels like a warm, sticky embrace that clings to your skin, making it necessary to stay hydrated while exploring the sights.

May Average Humidity in Helena

This chart illustrates the average monthly humidity levels in Helena, 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 Helena is approximately 82%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec75%76%67%70%82%82%81%76%67%72%80%83%
Data source: Humidity data for May generated using information from the Copernicus Climate Change Service.

May UV Index in Helena

In Helena in May, the maximum UV index reaches 11, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's essential to take precautions. For more details, you can check the Hourly UV Index in Helena.

Maximum UV Index Levels in Helena for May

The chart shows the monthly maximum UV Index (UVI) for Helena 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 Helena typically reaches 11, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec46810111111109753
Data source: Helena 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 Helena Compares to Other Months

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

This table compares monthly weather conditions in Helena, showing how May’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather3°C (37°F)35 mm (1.4 inches)75%moderate
February Weather3°C (38°F)24 mm (1.0 inches)76%high
March Weather11°C (52°F)77 mm (3.0 inches)67%very high
April Weather15°C (59°F)82 mm (3.2 inches)70%very high
May Weather20°C (69°F)143 mm (5.6 inches)82%extreme
June Weather26°C (80°F)112 mm (4.4 inches)82%extreme
July Weather28°C (83°F)45 mm (1.8 inches)81%extreme
August Weather27°C (81°F)69 mm (2.7 inches)76%very high
September Weather24°C (76°F)59 mm (2.3 inches)67%very high
October Weather16°C (61°F)86 mm (3.4 inches)72%high
November Weather9°C (49°F)21 mm (0.8 inches)80%moderate
December Weather5°C (42°F)29 mm (1.2 inches)83%moderate

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