Stillwater Weather in September

The climate in Stillwater during September can be summarized as mild and a little damp.

September is in the fall / autumn in Stillwater and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 22°C (71°F), whilst at night 9°C (48°F) is normal.

On average September is the 5th wettest month of the year in Stillwater with around 80mm 3.2 inches of rain making it a a little damp time to visit. This rainfall is typically spread over 10 days, although this may vary considerably.

On the flip side this corresponds to an average of 8 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 Stillwater in September 2025.