Gillette Weather in September

What's the weather like in Gillette (Wyoming) in September 2025?

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

September is in the fall / autumn in Gillette and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 23°C (73°F), whilst at night 6°C (42°F) is normal.

Gillette weather averages (imperial / metric)
Daytime temperature	23°C 73.3°F
Nightly temperature	5.5°C 41.8°F
Average temperature	14.2°C 57.6°F
Daily sunshine	9.3 hrs
Avg rainfall	31 mm 1.2 ins
Rainy days	8 days
Sea temperature	15.5°C 59.8°F
Humidity	53%
Windspeed	16.2kph 10 mph

On average September is the 6th wettest month of the year in Gillette with around 31mm 1.2 inches of rain making it a reasonably dry time to visit. This rainfall is typically spread over 8 days, although this may vary considerably.

On the flip side this corresponds to an average of 9.3 hours of sunshine per day.

September temperatures in Gillette

Gillette average temperature in September

September rainfall

September hourly sunshine

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 Gillette in September 2025.