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How is the Weather in Philadelphia During September?

Updated: July 31, 2023

September features warm to comfortable afternoons with cool late nights and early mornings near the end of this month. About 7-8 days will be considered humid, mostly early in the month.


Daytime high temperatures tend to average near 81-82 F (27-28 C) early in September, cooling down to around 73-75 F (23-24 C) near the end of the month. 

You can expect about 2 days, mostly early in the month, to reach or exceed 90 F (32 F). The record high temperature in Philadelphia during September is 100 F (37.8 C). 

Late night and early morning lows tend to average around 63-65 F (17-18 C) early in the month, cooling down to about 55-59 F (13-15 C) near the end of the month.

A few of the cooler mornings, especially later in the month, can dip down to near 45 F (7 C). The record low temperature in Philadelphia during September is 35 F (1.7 C).

Sky and Rain

You can expect, on average, about 10 mostly sunny, 9 partly sunny, and 11 mostly cloudy days this month. 

About 8-9 days will record some measurable rainfall, however, only 2-3 or these days receive 0.5 inches (12.7 mm) or more of rain.

You can also expect thunderstorms during about 2 days this month. 


The number of daylight hours decreases rapidly this month from about 13.1 hours on the 1st down to 11.8 hours by the 30th.


Wind speeds generally are light to gentle during September, averaging 4-12 mph (6-19 kph) with briefly higher gusts during thunderstorms. 

What to Wear in Philadelphia During September?

Summer-like weather prevails early this month, however, a taste of Autumn should be expected towards the end of the month.

You should pack light summer clothes but also pack some warmer tops, as well as a windbreaker or light jacket for the cooler days.

You should also pack both long and short-sleeve tops, jeans, sneakers and some comfortable walking shoes. A light rain jacket or umbrella will come in handy for the rainy days.

Things to Do in Philadelphia in September

Although autumn is right around the corner, it should still be quite warm throughout the month of September, making this a great time to take a pay-what-you-wish Philadelphia walking tour.

The Philadelphia Phillies will also be nearing the end of their season, and there's a good chance they'll be playing some important games in the lead up to the postseason.

In addition to baseball, you'll also have a few opportunities to see the Philadelphia Eagles play some early season football games.

The Off-Broadway production of The Lion King will also be taking place this month from September 1st - 9th, 2023.

For more ideas, make sure to read our full post on things to do in Philadelphia.

Fred Pickhardt  
Ocean Weather Services 

About The Author

Fred Pickhardt

Fred is a marine meteorologist and sailed briefly with American Export Lines in the Far East trade. He has extensive experience in weather analysis, weather forecasting, and forensic weather event reconstructions. Fred founded Ocean Weather Services and currently provides forensic marine weather reports to the maritime industry.
Updated: July 31st, 2023
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