Mount Vernon Weather in September

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

September is in the fall / autumn in Mount Vernon and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 20°C (68°F), whilst at night 9°C (48°F) is normal.

On average September is the 5th driest month of the year in Mount Vernon with around 52mm 2 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 Mount Vernon in September 2025.