Great Falls weather in September 2025

Expect 21°C daytime maximum temperatures in the shade with on average 8 hours of sunshine per day in Great Falls in September. Check more long-term weather averages for Great Falls in September before you book your next holiday to Montana in 2025/2026.

  • 21°C maximum daytime temperature in September in Great Falls21
    21°C max day temperature
  • 8 hours of sunshine per day
  • 7 days with some rainfall in September in Great Falls7
    7 days with some rainfall
  • 6°C minimum night-time temperature in September in Great Falls6
    6°C min night temperature
  • 13 hours of daylight per day in September in Great Falls13
    13 hours of daylight per day
  • No heat & humidity in September in Great Falls0
    No heat & humidity
  • 26 mm monthly rainfall in September in Great Falls26
    26 mm of monthly rainfall
  • UV (maximum) index 5 (Moderate) in September in Great Falls5
    5 (Moderate) UV index

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The September weather guide for Montana (Great Falls) shows long term weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.

Metric (°C / mm)  |  Imperial (°F / inches)

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How hot is it in Great Falls in September?

Daytime temperatures usually reach 21°C in Great Falls in September, falling to 6°C at night.

How sunny is it in Great Falls in September?

There are normally 8 hours of bright sunshine each day in Great Falls in September - that's 66% of daylight hours.

Does it rain in Great Falls in September?

There are usually 7 days with some rain in Great Falls in September and the average monthly rainfall is 26mm.

Great Falls September sunrise & sunset times

Browse the sunrise and sunset times for Great Falls in September 2025. Select a month to view Great Falls sunrise and sunset times for the next 12 months.

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Monday, 1st September 2025 05:44 19:05
Monday, 15th September 2025 06:03 18:36
Tuesday, 30th September 2025 06:23 18:06

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