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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 (73°F). Expect a minimum of 8°C (47°F) and a maximum of 34°C (94°F), offering a wide range of comfort. Be prepared for occasional showers, with 77 mm (3.0 in) of precipitation over 7 days. With an average humidity of 79%, you'll feel the warmth and moisture in the air.

September Temperature in Princeton

In September in Princeton, the average temperature is 23°C (73°F), with maximums reaching 34°C (94°F) and minimums dropping to as low as 8°C (47°F). This pleasant climate makes it an ideal time for travelers to explore and enjoy outdoor activities.

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 (73°F), with highs reaching up to 34°C (94°F) and lows dropping to around 8°C (47°F).
JanFebMarAprMayJunJulAugSepOctNovDec353848566877807773614541
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 77 mm (3.0 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 77 mm (3.0 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec9511914611813112473877711193102
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 79%. With an average temperature of 23°C (73°F), this humidity feels like a warm embrace that clings to the skin, making travel feel both invigorating and slightly exhausting as the air wraps around you like a damp blanket.

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 79%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%82%84%83%80%83%82%83%79%79%88%87%
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.
JanFebMarAprMayJunJulAugSepOctNovDec3571010111099743
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 Weather1°C (35°F)95 mm (3.7 inches)84%moderate
February Weather3°C (38°F)119 mm (4.7 inches)82%moderate
March Weather9°C (48°F)146 mm (5.7 inches)84%high
April Weather14°C (57°F)118 mm (4.6 inches)83%very high
May Weather20°C (69°F)131 mm (5.2 inches)80%very high
June Weather25°C (77°F)124 mm (4.9 inches)83%extreme
July Weather27°C (80°F)73 mm (2.9 inches)82%very high
August Weather25°C (78°F)87 mm (3.4 inches)82%very high
September Weather23°C (73°F)77 mm (3.0 inches)79%very high
October Weather16°C (61°F)111 mm (4.4 inches)79%high
November Weather7°C (45°F)92 mm (3.6 inches)88%moderate
December Weather5°C (41°F)102 mm (4.0 inches)87%moderate

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