September Weather in Princeton, United States

Last updated: June 24, 2025

In September, the average temperature in Princeton, United States is a pleasant 21°C (70°F), with a minimum dipping to 6°C (44°F) and a maximum soaring to 33°C (92°F). Expect some rain, as 119 mm (4.7 in) of precipitation typically falls over 8 days. The average humidity hovers around 73%, making for a comfortably warm atmosphere.

September Temperature in Princeton

In September in Princeton, the average temperature is 21°C (70°F). Maximum can reach 33°C (92°F) and minimum can be as low as 6°C (44°F). This makes it a great time to visit Princeton, offering pleasant weather for outdoor activities while also allowing for cooler evenings.

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

The chart illustrates September temperature patterns in Princeton, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Princeton, September typically has an average temperature of 21°C (70°F), with highs reaching up to 33°C (92°F) and lows dropping to around 6°C (44°F).

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

September Precipitation in Princeton

In Princeton in September, the precipitation amount is 119 mm (4.7 in) over a span of 8 days.

September Precipitation Trends in Princeton

The chart displays monthly precipitation patterns in Princeton, 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 Princeton, September typically receives around 119 mm (4.7 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 Princeton

In Princeton in September, humidity is 73%. With an average temperature of 21°C (70°F), this humidity feels like a warm embrace that can make outdoor activities feel sweltering, so it's essential to stay hydrated and take breaks in the shade while exploring.

September Average Humidity in Princeton

This chart illustrates the average monthly humidity levels in Princeton, 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 Princeton is approximately 73%, 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 Princeton

In Princeton in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in Princeton.

Maximum UV Index Levels in Princeton for September

The chart shows the monthly maximum UV Index (UVI) for Princeton 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 Princeton typically reaches 8, which falls under the very high exposure category.

Data source: Princeton 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 Princeton Compares to Other Months

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

This table compares monthly weather conditions in Princeton, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-4°C (26°F)	48 mm (1.9 inches)	78%	moderate
February Weather	-2°C (28°F)	44 mm (1.7 inches)	80%	moderate
March Weather	6°C (42°F)	103 mm (4.0 inches)	77%	high
April Weather	10°C (51°F)	78 mm (3.1 inches)	77%	very high
May Weather	18°C (64°F)	158 mm (6.2 inches)	77%	very high
June Weather	24°C (76°F)	124 mm (4.9 inches)	81%	extreme
July Weather	26°C (78°F)	106 mm (4.2 inches)	81%	extreme
August Weather	24°C (75°F)	88 mm (3.5 inches)	77%	very high
September Weather	21°C (70°F)	119 mm (4.7 inches)	73%	very high
October Weather	12°C (54°F)	154 mm (6.1 inches)	75%	high
November Weather	5°C (40°F)	55 mm (2.2 inches)	85%	moderate
December Weather	1°C (34°F)	34 mm (1.4 inches)	83%	moderate