September weather forecastWilmington, DE
September
Weather in September
September in Wilmington signifies an onset of fall with declining temperatures, yet preserving the warmth of the passing summer. September paves the way for decreased rainfall compared with the wet August, registering only 2.4" (61mm). Moving forward into October, the city experiences further drops in temperature and the initial intimations of winter with the reemergence of snowfall.Temperature
The beginning of September in Wilmington subtly marks a decrease in the average high-temperature, transitioning from a warm 82.9°F (28.3°C) in August to a still moderately hot 76.3°F (24.6°C). Wilmington's nighttime temperature in September falls to an average of 59.9°F (15.5°C).Humidity
The average relative humidity in September in Wilmington is 77%.Rainfall
In Wilmington, in September, it is raining for 13.3 days, with typically 2.4" (61mm) of accumulated precipitation. Throughout the year, there are 168.9 rainfall days, and 35.55" (903mm) of precipitation is accumulated.Snowfall
In Wilmington, snow does not fall in June through September.Ocean temperature
In September, the average ocean temperature is 69.8°F (21°C).Note: For most, swimming in 69.8°F (21°C) is not an enjoyable activity. Furthermore, controlling your breathing becomes progressively more difficult as the water temperature decreases from 69.8°F (21°C) to 59°F (15°C).
Daylight
The average length of the day in September in Wilmington is 12h and 26min.On the first day of September, sunrise is at 6:30 am and sunset at 7:32 pm. On the last day of the month, sunrise is at 6:58 am and sunset at 6:45 pm EDT.
Sunshine
In September, the average sunshine in Wilmington, Delaware, is 8.8h.UV index
The average daily maximum UV index in September in Wilmington is 4. A UV Index estimate of 3 to 5 represents a medium health hazard from exposure to the Sun's UV radiation for ordinary individuals.Note: A maximum high UV index of 4 in September translates into the following recommendations:
Put precautions into practice - Protective measures against sun-induced damage are advised. Considering the harmful UV rays from the Sun during midday, it's essential to reduce exposure. Your best bet for sun defense on the face, eyes, and neck is a hat with a wide brim.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Wilmington, DE
- Average high temperature in September: 76.3°F
The warmest month (with the highest average high temperature) is July (84.9°F).
The month with the lowest average high temperature is January (37°F).
- Average low temperature in September: 59.9°F
The month with the highest average low temperature is July (68.4°F).
The coldest month (with the lowest average low temperature) is January (25.3°F).
Average pressure in September
Wilmington, DE
- Average pressure in September: 30.05"Hg
The month with the highest atmospheric pressure is November (30.12"Hg).
The month with the lowest atmospheric pressure is June (29.94"Hg).
Average wind speed in September
Wilmington, DE
- Average wind speed in September: 5.8mph
The windiest months (with the highest average wind speed) are January, February and March (8.6mph).
The calmest month (with the lowest average wind speed) is August (5.4mph).
Average humidity in September
Wilmington, DE
- Average humidity in September: 77%
The month with the highest relative humidity is October (78%).
The month with the lowest relative humidity is April (72%).
Average rainfall in September
Wilmington, DE
- Average rainfall in September: 2.4"
The wettest month (with the highest rainfall) is August (4.09").
The driest month (with the least rainfall) is January (2.36").
Average rainfall days in September
Wilmington, DE
- Average rainfall days in September: 13.3 days
The month with the highest number of rainy days is May (18.7 days).
The month with the least rainy days is November (8.8 days).
Average snowfall in September
Wilmington, DE
- Average snowfall in September: 0"
The month with the highest snowfall is March (3.58").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Wilmington, DE
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (6.8 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average sea temperature in September
Wilmington, DE
- Average sea temperature in September: 70°F
The best month for swimming (with the highest average sea temperature) is August (73°F).
The coldest month (with the lowest average sea temperature) is February (34°F).
Average daylight in September /
Average sunshine in September
Wilmington, DE
- Average daylight in September: 12h and 24min
The month with the longest days is June (Average daylight: 14h and 54min).
The month with the shortest days is December (Average daylight: 9h and 24min).
- Average sunshine in September: 8h and 48min
The month with the most sunshine is July (Average sunshine: 10h and 36min).
The month with the least sunshine is February (Average sunshine: 4h and 54min).
Average sunshine days in September
Wilmington, DE
- Average sunshine days in September: 14.2 days
The month with the most sunshine days is November (18.6 days).
The months with the least sunshine days are May and July (9.8 days).
Average UV index in September
Wilmington, DE
- Average UV index in September: 4
The months with the highest UV index are May, June, July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in September
Wilmington, DE
- Average cloud cover in September: 37
The months with the most cloud cover are February and March (Cloud cover 47).
The month with the least cloud cover is July (Cloud cover 31).
Average visibility in September
Wilmington, DE
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
