Roundup Weather in September

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

The climate in Roundup during September can be summarized as mild and reasonably dry.

September is in the fall / autumn in Roundup and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 22°C (72°F), whilst at night 6°C (43°F) is normal.

Roundup weather averages (imperial / metric)
Daytime temperature 22.1°C 71.8°F
Nightly temperature 6.1°C 43°F
Average temperature 14.1°C 57.4°F
Daily sunshine 9.2 hrs
Avg rainfall 35 mm 1.4 ins
Rainy days 7 days
Sea temperature 14.1°C 57.4°F
Humidity 53%
Windspeed 16.6kph 10 mph

On average September is the 4th wettest month of the year in Roundup with around 35mm 1.4 inches of rain making it a reasonably 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 9.2 hours of sunshine per day.

September temperatures in Roundup

Roundup average temperature in September

September rainfall

Roundup average rain in September

September hourly sunshine

Roundup 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 Roundup 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

Roundup weather stats

Roundup weather statistics
Hottest month: July 29.5°C 85.1°F
Driest month: February 13mm 0.5ins
Sunniest month: July 12.7hrs
Coldest month: January -0.3°C 31.5°F
Wettest month: May 73mm 2.9ins
Map showing location of Roundup (46.44524, -108.5418) Roundup map pin © Google

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