Wilmington, DE weather in September
September in Wilmington: mild, with some rain. Highs 79°F, lows 59°F, rain on about 9 days. A good month for most outdoor plans.
- Normal high
- 79°F
- Normal low
- 59°F
- Wet days
- 9
- 4.4 in total
- Muggy days
- 7
- dew point 65°F+
How September changes from start to finish
| September 1 | September 30 | |
|---|---|---|
| Normal high | 83°F | 73°F |
| Normal low | 64°F | 54°F |
| Chance of a wet day | 27% | 31% |
| Sunrise / sunset | 6:30 am / 7:34 pm | 6:57 am / 6:46 pm |
| Daylight | 13.1 h | 11.8 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Eastern Time).
A typical September day
- 6 am64°Fdew point 58°F
- 9 am70°Fdew point 59°F
- Noon75°Fdew point 58°F
- 3 pm77°Fdew point 57°F
- 6 pm74°Fdew point 58°F
- 9 pm69°Fdew point 59°F
NOAA hourly normals (local standard time) from Philadelphia Intl Airport (19 mi away); average wind 8 mph; clear or few clouds in 62% of daytime hours, mostly cloudy or overcast in 31%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F13 of 30
- Beach dayshigh 80-95°F, under 0.05 in of rain, afternoon wind under 15 mph10 of 30
- Hot dayshigh 90°F or more2 of 30
- Muggy daysdaily mean dew point 65°F or more7 of 30
- Wet daysat least 0.01 in of rain or melted snow9 of 30
- Notable rainat least 0.10 in6 of 30
- Freezing nightslow 32°F or below0 of 30
- Snow on the groundsnow depth 1 in or more0 of 30
Average days per September, counted from daily records for each year 1991-2020.
Rain in September
Normal precipitation is 4.4 in; a dry September brings about 2.2 in and a wet one about 5.9 in (25th and 75th percentiles). About 3 days bring half an inch or more, and about 1 an inch or more.
How September varies from year to year
- Warmest September, 1991-20202005: average high 83°F
- Coolest September2006: average high 74°F
- Wettest September1999: 12.7 in
- Driest September2005: 0.4 in
- Highest reading97°F (September 3, 1993)
- Lowest reading37°F (September 25, 1997)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
September compared with August and October
| August | September | October | |
|---|---|---|---|
| Normal high | 85°F | 79°F | 67°F |
| Normal low | 67°F | 59°F | 47°F |
| Wet days | 9 | 9 | 9 |
| Comfortable days | 3 | 13 | 14 |
| Daylight | 13.7 h | 12.4 h | 11.1 h |
Highs change by -6°F from August and -12°F into October.
Nearby alternatives in September
- Cooler: Montauk, NY209 mi · high 73°F · 10 wet days
How Wilmington ranks in September
- Normal high215th warmest of 378 cities; 2nd of 2 in Delaware
- Wet days234th driest of 378
- Comfortable days127th most of 342
What to pack for Wilmington in September
- A rain jacket or umbrella – rain on about 9 days
- A swimsuit – about 10 beach days
Heating and cooling
September has 38 heating degree days and 155 cooling degree days (base 65°F), 3% of the year's total heating and cooling demand.
Questions
How hot is Wilmington in September?
The normal high is 79°F and the normal low is 59°F. From 1991 to 2020 the hottest September reading was 97°F (September 3, 1993).
Does it rain a lot in Wilmington in September?
About 9 days in September have at least 0.01 in of precipitation, and the normal total is 4.4 in. The wettest September in 1991-2020 was in 1999 (12.7 in); the driest was in 2005 (0.4 in).
Is September a good time to visit Wilmington?
September ranks 3rd of 12 months on our comfort score for Wilmington (64 out of 100). It has about 13 comfortable days and about 2 days at 90°F or hotter. The best month is May.
Where the numbers come from
- Temperature, rain, snowfall and snow depth: Wilmington New Castle Co Airport (USW00013781), 5.8 mi SSW of the city center, 79 ft . NOAA normals and daily records, 1991-2020.
- Frost dates: Wilmington Porter Rsch (USC00079605), 1.9 mi N of the city center, 270 ft (179 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Humidity and wind by hour: Philadelphia Intl Airport (USW00013739), 19 mi ENE of the city center, 10 ft (81 ft lower than the city). NOAA normals and daily records, 1991-2020.
- Cloud cover: Millville Muni Airport (USW00013735), 37 mi SE of the city center, 70 ft . NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Philadelphia International Airport (724080-13739), 19 mi ENE of the city center, 7 ft (84 ft lower than the city). Hourly observations, 1991-2020.