Philadelphia, PA weather in September
Philadelphia is mild in September, with some rain: highs average 79°F and nights drop to about 61°F. Expect about 9 wet days. A good month for most outdoor plans.
- Normal high
- 79°F
- Normal low
- 61°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 | 84°F | 74°F |
| Normal low | 65°F | 56°F |
| Chance of a wet day | 28% | 32% |
| Sunrise / sunset | 6:28 am / 7:32 pm | 6:56 am / 6:45 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 (7 mi away); average wind 8 mph; clear or few clouds in 62% of daytime hours, mostly cloudy or overcast in 30%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F12 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 2.7 in and a wet one about 5.4 in (25th and 75th percentiles). About 2 days bring half an inch or more, and about 1 an inch or more.
How September varies from year to year
- Warmest September, 1991-20202015: average high 84°F
- Coolest September2000: average high 75°F
- Wettest September1999: 13.1 in
- Driest September2005: 0.2 in
- Highest reading96°F (September 3, 2015)
- Lowest reading41°F (September 30, 2000)
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 | 86°F | 79°F | 67°F |
| Normal low | 68°F | 61°F | 49°F |
| Wet days | 9 | 9 | 9 |
| Comfortable days | 3 | 12 | 15 |
| Daylight | 13.7 h | 12.4 h | 11.1 h |
Highs change by -7°F from August and -12°F into October.
Nearby alternatives in September
- Cooler: Montauk, NY184 mi · high 73°F · 10 wet days
How Philadelphia ranks in September
- Normal high211th warmest of 378 cities; 1st of 4 in Pennsylvania
- Wet days273rd driest of 378
- Comfortable days131st most of 342
What to pack for Philadelphia in September
- A rain jacket or umbrella – rain on about 9 days
Heating and cooling
September has 28 heating degree days and 175 cooling degree days (base 65°F), 3% of the year's total heating and cooling demand.
Questions
How hot is Philadelphia in September?
The normal high is 79°F and the normal low is 61°F. From 1991 to 2020 the hottest September reading was 96°F (most recently on September 3, 2015).
Does it rain a lot in Philadelphia 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 (13.1 in); the driest was in 2005 (0.2 in).
Is September a good time to visit Philadelphia?
September ranks 4th of 12 months on our comfort score for Philadelphia (64 out of 100). It has about 12 comfortable days and about 2 days at 90°F or hotter. The best month is May.
Where the numbers come from
- Temperature, rain, snowfall, snow depth and humidity and wind by hour: Philadelphia Intl Airport (USW00013739), 6.8 mi SSW of the city center, 10 ft . NOAA normals and daily records, 1991-2020.
- Frost dates: Phila Franklin Inst (USC00366886), 0.6 mi NW of the city center, 60 ft . NOAA normals and daily records, 1991-2020.
- Cloud cover: Philadelphia Ne Airport (USW00094732), 12 mi NE of the city center, 100 ft (65 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Philadelphia International Airport (724080-13739), 6.4 mi SSW of the city center, 7 ft . Hourly observations, 1991-2020.