Philadelphia weather in September
September in Philadelphia: warm, rainy, with clean air — one of the best months to visit.
#2 of 12 months in Philadelphia · #177 of 604 destinations to visit in September · comfort 86/100 (tier A)
Updated June 2026 · climate normals from ERA5 reanalysis
Philadelphia climate normals — September
| Daytime high | 26°C / 78°F | 🌤 warm |
|---|---|---|
| Nighttime low | 17°C / 63°F | |
| Feels like (high) | 26°C / 79°F | |
| Rainfall | 96 mm / 3.8 in | 🌧 rainy |
| Rainy days | 9 days | |
| Humidity | 70% | 💧 humid |
| Dew point | 15°C / 58°F | |
| Sunshine | 9 h/day | |
| Daylight | 12.4 h | |
| Wind | 15 km/h / 9 mph | |
| Air quality (US AQI) | 45 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Philadelphia in September — FAQ
- Is September a good time to visit Philadelphia?
- September in Philadelphia: warm, rainy, with clean air — one of the best months to visit. It ranks #2 of 12 months for Philadelphia on SeasonMap's comfort score (86/100).
- What is the weather like in Philadelphia in September?
- In September, Philadelphia averages a daily high of 25.6°C and a low of 17.1°C, with about 95.5 mm of rain over roughly 9 rainy days.
- What is the air quality in Philadelphia in September?
- Philadelphia has a mean US Air Quality Index of about 45 in September.