Great Falls Weather in September

What's the weather like in Great Falls (Montana) in September 2025?

The climate in Great Falls during September can be summarized as mild and dry.

September is in the fall / autumn in Great Falls and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 21°C (70°F), whilst at night 6°C (43°F) is normal.

Great Falls weather averages (imperial / metric)
Daytime temperature 20.9°C 69.6°F
Nightly temperature 6.3°C 43.3°F
Average temperature 13.6°C 56.5°F
Daily sunshine 9.1 hrs
Avg rainfall 26 mm 1 ins
Rainy days 7 days
Sea temperature 13.3°C 56°F
Humidity 54%
Windspeed 16.9kph 11 mph

On average September is the 6th wettest month of the year in Great Falls with around 26mm 1 inches of rain making it a dry time to visit. This rainfall is typically spread over 7 days, although this may vary considerably.

On the flip side this corresponds to an average of 9.1 hours of sunshine per day.

September temperatures in Great Falls

Great Falls average temperature in September

September rainfall

Great Falls average rain in September

September hourly sunshine

Great Falls average rain in September

The data used in these monthly averages covers a period of over 100 years right up until last year. As such they are a valid prediction of what to expect for the weather in Great Falls in September 2025.

Other monthly averages

Best places to visit in September

UV index Best time to go?

Beta

Current (hourly) weather 15 day forecast

Great Falls weather stats

Great Falls weather statistics
Hottest month: July 27.8°C 82°F
Driest month: February 14mm 0.6ins
Sunniest month: July 13.1hrs
Coldest month: January -1.7°C 28.9°F
Wettest month: June 71mm 2.8ins
Map showing location of Great Falls (47.50024, -111.30081) Great Falls map pin © Google

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