Philadelphia weather in September
Temperature, sea and sunshine in September: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in September
Good
Best time to visit: April – June, August – October
What is the weather like in Philadelphia in September?
In September, Philadelphia is warm: daytime highs average 25 °C, and nights cool down to about 16 °C. The sea averages 22.9 °C – refreshing for a swim. Expect around 6 hours of sunshine a day. Rain falls on about 9 days, adding up to 96 mm. All in all, September is a good month for a holiday in Philadelphia.
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 67 | 79 | 79 |
| Day | 29° | 25° | 19° |
| Night | 20° | 16° | 10° |
| Sea | 25° | 23° | 18° |
| Sun | 7 h | 6 h | 5 h |
| Rain days | 11 | 9 | 8 |
More details for September
- Daylight
- 12 h 31 min06:40 – 19:12
- UV index
- 6 · highclear sky, noon (estimate)All months
- Muggy days
- 8 daysdew point 18 °C or moreAll months
- Wind
- 15 km/haverage daily peakAll months
- Cloud cover
- 53 %on averageAll months
- Hot days
- 3 days30 °C or moreAll months
- Snow days
- 0 days1 cm or more of fresh snowAll months
- Time zone
- UTC−4America/New_York
How the score comes together
- Temperatureweight 50 %100 %
- Sunshineweight 20 %47 %
- Few rainy daysweight 30 %65 %
Each factor is rated from 0 to 100 % and weighted for the travel style “City break”.
What to pack in September
- Swimwear
- Sunscreen
- Sunglasses & sun hat
- Light, breathable clothes
- Rain jacket or umbrella
Philadelphia in September: quick answers
Is Philadelphia hot in September?
Warm rather than hot: in September, daytime highs in Philadelphia average 25 °C and nights cool to about 16 °C. On about 3 days the thermometer climbs to 30 °C or more.
Can you swim in Philadelphia in September?
Yes. In September the sea averages 22.9 °C – refreshing for a swim.
Does it rain much in Philadelphia in September?
Rain falls on about 9 days, adding up to 96 mm.
Philadelphia month by month
The whole year in PhiladelphiaAll destinations: USAWhere to go in SeptemberSea temperature in September
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0). Sources & licences