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.

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• Wilmington - September »
  In Wilmington the average seawater temperature in September is 69.8°F (21°C). On the first day of September in Wilmington sunrise is at 6:30 am and sunset at 7:34 pm.
• Dover - September »
  In Dover, in September, it is raining for 12.9 days, with typically 1.89" (48mm) of accumulated precipitation. In Dover, in September, during 12.9 rainfall days, 1.89" (48mm) of precipitation is typically accumulated.
• Newark - September »
  In Newark during September, the rain falls for 13.7 days and regularly aggregates up to 2.36" (60mm) of precipitation. In Newark, during September, the rain falls for 13.7 days and regularly aggregates up to 2.36" (60mm) of precipitation.
• Middletown - September »
  An average minimum temperature of 61°F (16.1°C) marks the month of September in Middletown, Delaware. On the first day of September in Middletown, sunrise is at 6:31 am and sunset at 7:34 pm.
• Smyrna - September »
  September in Smyrna represents a transition phase from summer to fall with temperatures dipping further from August's readings. On the first day of September in Smyrna, sunrise is at 6:30 am and sunset at 7:33 pm.
• Milford - September »
  On the last day of September, in Milford, sunrise is at 6:56 am and sunset at 6:46 pm EDT. In Milford, in September, it is raining for 13.5 days, with typically 1.85" (47mm) of accumulated precipitation.
• Seaford - September »
  May, August and September, with an average relative humidity of 80%, are most humid months in Seaford, Delaware. In Seaford, Delaware, 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 first day of September in Georgetown, sunrise is at 6:30 am and sunset at 7:32 pm.
• 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, sunrise is at 6:30 am and sunset at 7:34 pm.
• New Castle - September »
  On the first day of September in New Castle, Delaware, sunrise is at 6:30 am and sunset at 7:34 pm. On the first day of September in New Castle sunrise is at 6:30 am and sunset at 7:34 pm.
• Lewes - September »
  In Lewes in September, it is raining for 14.8 days, with typically 2.68" (68mm) of accumulated precipitation. In Lewes the average seawater temperature in September is 72.9°F (22.7°C).
• Rehoboth Beach - September »
  In Rehoboth Beach in September, it is raining for 7.5 days, with typically 0.28" (7mm) of accumulated precipitation. On the first day of September in Rehoboth Beach, sunrise is at 6:29 am and sunset at 7:31 pm.