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September Weather in Helena Valley Northwest, United States

Last updated: June 24, 2025

In September, the average temperature in Helena Valley Northwest, United States hovers around 14°C (57°F). Temperatures can vary dramatically, with a minimum drop to -4°C (25°F) and a maximum rise to 33°C (92°F). Expect approximately 37 mm (1.5 in) of precipitation spread over 6 days, and enjoy a comfortable average humidity level of 68%.

September Temperature in Helena Valley Northwest

In September in Helena Valley Northwest, the average temperature is 14°C (57°F). Maximums can reach 33°C (92°F), while minimums can dip as low as -4°C (25°F). Travelers should prepare for a wide range of temperatures and pack accordingly.

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

The chart illustrates September temperature patterns in Helena Valley Northwest, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Helena Valley Northwest, September typically has an average temperature of 14°C (57°F), with highs reaching up to 33°C (92°F) and lows dropping to around -4°C (25°F).
JanFebMarAprMayJunJulAugSepOctNovDec211831385060696757413224
Data source: Temperature data for Helena Valley Northwest 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 Valley Northwest

In Helena Valley Northwest in September, the precipitation amount is 37 mm (1.5 in) over the course of 6 days.

September Precipitation Trends in Helena Valley Northwest

The chart displays monthly precipitation patterns in Helena Valley Northwest, 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 Valley Northwest, September typically receives around 37 mm (1.5 inches) of precipitation spread over approximately 6 days.
JanFebMarAprMayJunJulAugSepOctNovDec194430596478172337352930
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Helena Valley Northwest

In Helena Valley Northwest in September, humidity is 68%. With an average temperature of 14°C (57°F), this humidity feels like a mild embrace, making travel enjoyable yet occasionally a bit sticky, ideal for leisurely strolls but requiring a light layer for comfort.

September Average Humidity in Helena Valley Northwest

This chart illustrates the average monthly humidity levels in Helena Valley Northwest, 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 Valley Northwest is approximately 68%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec87%88%83%78%76%78%77%71%68%72%84%91%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Helena Valley Northwest

In Helena Valley Northwest in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in Helena Valley Northwest.

Maximum UV Index Levels in Helena Valley Northwest for September

The chart shows the monthly maximum UV Index (UVI) for Helena Valley Northwest 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 Valley Northwest typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec34689101098532
Data source: Helena Valley Northwest 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 Valley Northwest Compares to Other Months

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

This table compares monthly weather conditions in Helena Valley Northwest, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-6°C (22°F)19 mm (0.7 inches)87%moderate
February Weather-8°C (18°F)44 mm (1.7 inches)88%moderate
March Weather-1°C (31°F)30 mm (1.2 inches)83%high
April Weather4°C (39°F)59 mm (2.3 inches)78%very high
May Weather10°C (51°F)64 mm (2.5 inches)76%very high
June Weather16°C (60°F)78 mm (3.1 inches)78%very high
July Weather21°C (69°F)17 mm (0.7 inches)77%very high
August Weather20°C (67°F)23 mm (0.9 inches)71%very high
September Weather14°C (57°F)37 mm (1.5 inches)68%very high
October Weather5°C (41°F)35 mm (1.4 inches)72%moderate
November Weather0°C (32°F)29 mm (1.1 inches)84%moderate
December Weather-4°C (25°F)30 mm (1.2 inches)90%low

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