September Weather in Philadelphia, United States

Last updated: June 24, 2025

In Philadelphia, United States, the average temperature in September hovers around 24°C (75°F), making it a pleasant time to visit. However, be prepared for a range, as temperatures can dip to a cool 11°C (52°F) or soar up to a sizzling 36°C (97°F). Expect 92 mm (3.6 in) of precipitation spread over about 8 days, and a moderate humidity level of 76% that can add to the overall warmth.

September Temperature in Philadelphia

In September in Philadelphia, the average temperature is 24°C (75°F), with maximums reaching up to 36°C (97°F) and minimums dropping as low as 11°C (52°F). This makes it a great time for travelers to enjoy warm days while also being prepared for cooler evenings.

September Weather in Philadelphia: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Philadelphia, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Philadelphia, September typically has an average temperature of 24°C (75°F), with highs reaching up to 36°C (97°F) and lows dropping to around 11°C (52°F).

Data source: Temperature data for Philadelphia generated using information from the Copernicus Climate Change Service.

September Precipitation in Philadelphia

In Philadelphia in September, the precipitation amount is 92 mm (3.6 in), occurring over the course of 8 days.

September Precipitation Trends in Philadelphia

The chart displays monthly precipitation patterns in Philadelphia, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In Philadelphia, September typically receives around 92 mm (3.6 inches) of precipitation spread over approximately 8 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

September Humidity in Philadelphia

In Philadelphia in September, humidity is 76%. With an average temperature of 24°C (75°F), this humidity feels like a warm, enveloping blanket that clings to your skin, making outdoor activities feel a bit sluggish and urging you to seek shade and hydration.

September Average Humidity in Philadelphia

This chart illustrates the average monthly humidity levels in Philadelphia, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Philadelphia is approximately 76%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Philadelphia

In Philadelphia in September, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Philadelphia.

Maximum UV Index Levels in Philadelphia for September

The chart shows the monthly maximum UV Index (UVI) for Philadelphia in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in Philadelphia typically reaches 9, which falls under the very high exposure category.

Data source: Philadelphia September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

Extreme (11+): Avoid the sun, stay in shade.
Very High (8-10): Limit sun exposure.
High (6-7): Use SPF 30+ and protective clothing.
Moderate (3-5): Midday shade recommended.
Low (0-2): No protection needed.

How September Weather in Philadelphia Compares to Other Months

Weather in Philadelphia varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Philadelphia, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Philadelphia, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	6°C (42°F)	99 mm (3.9 inches)	86%	moderate
February Weather	8°C (47°F)	176 mm (6.9 inches)	86%	high
March Weather	12°C (53°F)	160 mm (6.3 inches)	86%	very high
April Weather	15°C (60°F)	141 mm (5.5 inches)	82%	very high
May Weather	21°C (70°F)	113 mm (4.4 inches)	85%	extreme
June Weather	24°C (76°F)	107 mm (4.2 inches)	85%	extreme
July Weather	26°C (80°F)	111 mm (4.4 inches)	83%	extreme
August Weather	26°C (78°F)	119 mm (4.7 inches)	76%	very high
September Weather	24°C (75°F)	92 mm (3.6 inches)	76%	very high
October Weather	18°C (65°F)	118 mm (4.6 inches)	80%	high
November Weather	10°C (50°F)	79 mm (3.1 inches)	88%	moderate
December Weather	8°C (46°F)	137 mm (5.4 inches)	88%	moderate