Thief River Falls Weather in September

The climate in Thief River Falls during September can be summarized as mild and reasonably dry.

September is in the fall / autumn in Thief River Falls and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 20°C (68°F), whilst at night 6°C (43°F) is normal.

On average September is the 5th wettest month of the year in Thief River Falls with around 60mm 2.4 inches of rain making it a reasonably dry time to visit. This rainfall is typically spread over 9 days, although this may vary considerably.

On the flip side this corresponds to an average of 7.2 hours of sunshine per day.

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 Thief River Falls in September 2025.