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September Weather in Princeton, United States

Last updated: June 24, 2025

In September, the average temperature in Princeton, United States is a pleasant 23°C (74°F). Prepare for a range as lows can dip to 11°C (52°F) while highs reach 34°C (93°F). During this month, expect 93 mm (3.7 in) of precipitation over about 7 days, contributing to an average humidity of 75%.

September Temperature in Princeton

In September in Princeton, the average temperature is 23°C (74°F). Maximums can reach 34°C (93°F) and minimums can be as low as 11°C (52°F). This pleasant climate makes Princeton an ideal destination for travelers seeking a comfortable getaway.

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 23°C (74°F), with highs reaching up to 34°C (93°F) and lows dropping to around 11°C (52°F).
JanFebMarAprMayJunJulAugSepOctNovDec384150586977817874634843
Data source: Temperature data for Princeton generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Princeton

In Princeton in September, the precipitation amount is 93 mm (3.7 in) over the course of 7 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 93 mm (3.7 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec971511351381191181061049310996119
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Princeton

In Princeton in September, humidity is 75%. With an average temperature of 23°C (74°F), this humidity feels like a warm, heavy blanket wrapping around you, making it feel more sweltering than it actually is, which can be quite uncomfortable for traveling.

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 75%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%84%84%80%82%83%80%76%75%75%85%88%
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 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 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 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec36710111110109753
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.
 TemperaturePrecipitationHumidityUV
January Weather3°C (38°F)97 mm (3.8 inches)86%moderate
February Weather5°C (42°F)150 mm (5.9 inches)84%high
March Weather10°C (51°F)135 mm (5.3 inches)84%high
April Weather14°C (58°F)138 mm (5.4 inches)80%very high
May Weather21°C (69°F)118 mm (4.7 inches)82%extreme
June Weather25°C (77°F)118 mm (4.6 inches)83%extreme
July Weather27°C (81°F)106 mm (4.2 inches)79%very high
August Weather26°C (78°F)104 mm (4.1 inches)76%very high
September Weather23°C (74°F)93 mm (3.7 inches)75%very high
October Weather17°C (63°F)108 mm (4.3 inches)74%high
November Weather9°C (48°F)96 mm (3.8 inches)85%moderate
December Weather6°C (44°F)119 mm (4.7 inches)88%moderate

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