Delaware Weather in September

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

September is in the fall / autumn in Delaware and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 25°C (76°F), whilst at night 11°C (52°F) is normal.

On average September is the 5th driest month of the year in Delaware with around 77mm 3 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 7.7 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 Delaware in September 2025.