September weather forecast
Delaware, USA

September in Delaware marks the beginning of the transition from hot summer to mild autumn. The month usually starts with summer's warmth but gradually leads into cooler and more pleasant conditions. The coastal regions, though still influenced by humidity, start to experience a decrease in temperature compared to the interior.

Temperatures in September begin to decline from the highs of 90°F (32.2°C) that were common in July and August. The nights become noticeably cooler, and the hot and humid periods of summer begin to wane.

Rainfall in September contributes to the annual total of 44" (1118mm) to 47" (1194mm), fitting into the relatively uniform distribution of precipitation throughout the year. Occasional storms may still occur, but they become less frequent as the month progresses.

The geographical features of Delaware, including the Atlantic Ocean and the Appalachian Mountains, continue to moderate the climate, but the impact of these features becomes more pronounced as the temperatures begin to cool.

Southern Delaware, known for its milder temperatures, starts to align more closely with the north as the growing season approaches its end.

September's weather is emblematic of a state in transition, moving from the full intensity of summer to the gentle embrace of autumn. The change is gradual but noticeable, and it carries with it a sense of anticipation for the colors and coolness of the coming fall season.

---

• Wilmington - September »
  In Wilmington in September, the average water temperature is 69.8°F (21°C). In Wilmington, snow does not fall in June through September.
• Dover - September »
  On the first day of September in Dover, Delaware, sunrise is at 6:31 am and sunset at 7:32 pm. In Dover, during September, the rain falls for 12.9 days and regularly aggregates up to 1.89" (48mm) of precipitation.
• Newark - September »
  May, September and October, with an average relative humidity of 78%, are most humid months in Newark, Delaware. In Newark in September, it is raining for 13.7 days, with typically 2.36" (60mm) of accumulated precipitation.
• Middletown - September »
  The months with the highest humidity in Middletown are May, June and September, with an average relative humidity of 78%. As September arrives, Middletown's weather displays a minor decrease in high-temperatures, transitioning from August's moderately hot 82.9°F (28.3°C) to a still warm 77°F (25°C).
• Smyrna - September »
  In Smyrna in September, it is raining for 14.3 days, with typically 2.32" (59mm) of accumulated precipitation. September in Smyrna represents a transition phase from summer to fall with temperatures dipping further from August's readings.
• Milford - September »
  In Milford, in September, during 13.5 rainfall days, 1.85" (47mm) of precipitation is typically accumulated. In September, in Milford, Delaware, the rain falls for 13.5 days.
• Seaford - September »
  The month with the least rainfall in Seaford, Delaware, is September, when the rain falls for 7.7 days and typically collects 0.39" (10mm) of precipitation. In Seaford in September, during 7.7 rainfall days, 0.39" (10mm) of precipitation is typically accumulated.
• Georgetown - September »
  In Georgetown in September, during 13.7 rainfall days, 1.81" (46mm) of precipitation is typically accumulated. On the last day of September, in Georgetown, sunrise is at 6:57 am and sunset at 6:45 pm EDT.
• Elsmere - September »
  In Elsmere in September, during 12 rainfall days, 1.73" (44mm) of precipitation is typically accumulated. On the first day of September in Elsmere, Delaware, sunrise is at 6:31 am and sunset at 7:33 pm.
• New Castle - September »
  On the first day of September in New Castle, Delaware, sunrise is at 6:31 am and sunset at 7:32 pm. In New Castle, during September, the rain falls for 11.2 days and regularly aggregates up to 1.42" (36mm) of precipitation.
• Lewes - September »
  In Lewes in September, during 14.8 rainfall days, 2.68" (68mm) of precipitation is typically accumulated. In Lewes, Delaware, the average seawater temperature in September is 72.9°F (22.7°C).
• Rehoboth Beach - September »
  The month with the least rainfall in Rehoboth Beach, Delaware, is September, when the rain falls for 7.5 days and typically collects 0.28" (7mm) of precipitation. On the first day of September in Rehoboth Beach, Delaware, sunrise is at 6:30 am and sunset at 7:30 pm.