Philadelphia weather in September
In September, Philadelphia has an average high of 26 °C79 °F and an average low of 15 °C59 °F, with about 102 mm4.0 in of precipitation. It is the 4th warmest month of the year and ranks 6th for precipitation.
How September compares with other months
Compared with August, September is 3.6 °C6.5 °F cooler on average and drier by 19 mm0.7 in. Compared with October, September is 6.9 °C12.3 °F warmer on average and drier by 8 mm0.3 in. Daylight lasts about 12.4 hours around the middle of the month. Average relative humidity is 74% and the average cloud amount 50%.
Is September a good time to visit Philadelphia?
Yes — September is one of the most comfortable months to visit Philadelphia by our comfort score, which favours average highs of 21–28 °C, lows above 5 °C, little rain and moderate humidity.
What to wear in September
For Philadelphia in September, pack light summer clothes such as T-shirts, shorts or light dresses, an extra layer for the cooler mornings and evenings and an umbrella or light rain jacket.
September in nearby places
| Place | High °C°F | Low °C°F | Precip. mmin |
|---|---|---|---|
| Philadelphia | 2679 | 1559 | 1024.0 |
| Allentown | 2678 | 1457 | 1194.7 |
| Atlantic City | 2475 | 1865 | 903.5 |
| Staten Island | 2678 | 1559 | 983.8 |
| Brooklyn | 2374 | 1864 | 973.8 |
| New York City | 2374 | 1864 | 973.8 |
| Paterson | 2679 | 1457 | 1094.3 |
| Manhattan | 2577 | 1559 | 1054.1 |
| Baltimore | 2780 | 1660 | 1134.5 |
Other months in Philadelphia
- January3 °C38 °F / −5 °C23 °F
- February5 °C41 °F / −4 °C24 °F
- March10 °C50 °F / −1 °C31 °F
- April17 °C63 °F / 5 °C41 °F
- May22 °C72 °F / 11 °C52 °F
- June27 °C81 °F / 17 °C62 °F
- July30 °C86 °F / 20 °C67 °F
- August30 °C85 °F / 19 °C66 °F
- September26 °C79 °F / 15 °C59 °F
- October19 °C67 °F / 8 °C47 °F
- November12 °C54 °F / 2 °C36 °F
- December7 °C44 °F / −2 °C28 °F
Frequently asked questions
How warm is Philadelphia in September?
In September the average high in Philadelphia is 26 °C (79 °F) and the average low is 15 °C (59 °F).
Does it rain a lot in Philadelphia in September?
On average about 102 mm (4.0 in) of precipitation falls in September; it ranks 6th of the 12 months.
Is September the warmest month in Philadelphia?
No. The warmest month in Philadelphia is July, with an average high of 30 °C (86 °F). The coldest month is January, with an average low of -5 °C (23 °F).
How long is the day in Philadelphia in September?
In the middle of September the day in Philadelphia lasts about 12.4 hours from sunrise to sunset. The value is calculated from the position of the city and the sun.
How humid is Philadelphia in September?
The average relative humidity in September is about 74%. Combined with warm days, it can feel muggy.
How cloudy is Philadelphia in September?
On average about 50% of the sky is covered by cloud in September. This is the mean cloud amount from satellite data, not the number of sunny days.
About this data
All figures are 25-year averages (January 2001 – December 2025) from the NASA POWER project. Temperature, humidity, wind and precipitation come from the MERRA-2 reanalysis (precipitation is the bias-corrected MERRA-2 product), cloud and solar values from CERES satellite data. They describe a grid cell of roughly 50–70 km, not a single weather station, so they can differ from airport records — most of all on coasts, in mountains and for rainfall. Average highs and lows are the monthly mean temperature plus/minus half of the average daily temperature range. Counts of rainy days are not part of this dataset.