Aspen Weather in September

The climate in Aspen during September can be summarized as cool and reasonably dry.

September is in the fall / autumn in Aspen and is typically the 4th warmest month of the year. Daytime maximum temperatures average around a cool 17°C (63°F), whilst at night -3°C (27°F) is normal.

On average September is the 6th driest month of the year in Aspen with around 44mm 1.7 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 9.4 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 Aspen in September 2025.