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September Weather in Helena, United States

Last updated: June 24, 2025

In September, the average temperature in Helena, United States is a comfortable 24°C (76°F), though it can swing from a brisk 7°C (45°F) to a sweltering 38°C (101°F). Expect a total precipitation of about 59 mm (2.3 in) spread over 6 days, with an average humidity level of 67%. Perfect for embracing the diverse weather this month has to offer!

September Temperature in Helena

In September in Helena, the average temperature is 24°C (76°F). Maximum temperatures can reach 38°C (101°F), while minimum temperatures can drop as low as 7°C (45°F). Travelers should prepare for warm days and cooler nights, making layering essential for comfort.

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

The chart illustrates September 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, September typically has an average temperature of 24°C (76°F), with highs reaching up to 38°C (101°F) and lows dropping to around 7°C (45°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.

September Precipitation in Helena

In Helena in September, the precipitation amount is 59 mm (2.3 in) over the course of 6 days.

September Precipitation Trends in Helena

The chart displays monthly precipitation patterns in Helena, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In Helena, September typically receives around 59 mm (2.3 inches) of precipitation spread over approximately 6 days.
JanFebMarAprMayJunJulAugSepOctNovDec35247782143112456959862129
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Helena

In Helena in September humidity is 67%. With an average temperature of 24°C (76°F), this humidity feels like a warm, steamy embrace, making travel slightly more challenging as you navigate through the thick air.

September Average Humidity in Helena

This chart illustrates the average monthly humidity levels in Helena, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Helena is approximately 67%, 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 September generated using information from the Copernicus Climate Change Service.

September UV Index in Helena

In Helena in September, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Helena.

Maximum UV Index Levels in Helena for September

The chart shows the monthly maximum UV Index (UVI) for Helena in September, 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 September, the maximum UV index in Helena typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec46810111111109753
Data source: Helena September 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 September 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 September’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 September’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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