Princeton Weather in September

What's the weather like in Princeton (Illinois) in September 2025?

The climate in Princeton during September can be summarized as warm and a little damp.

September is in the fall / autumn in Princeton and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 25°C (77°F), whilst at night 12°C (53°F) is normal.

Princeton weather averages (imperial / metric)
Daytime temperature 24.7°C 76.5°F
Nightly temperature 11.7°C 53.1°F
Average temperature 18.2°C 64.8°F
Daily sunshine 8.2 hrs
Avg rainfall 97 mm 3.8 ins
Rainy days 9 days
Sea temperature 18.8°C 65.9°F
Humidity 73%
Windspeed 14.4kph 9 mph

On average September is the 5th wettest month of the year in Princeton with around 97mm 3.8 inches of rain making it a a little damp time to visit. This rainfall is typically spread over 9 days, although this may vary considerably.

On the flip side this corresponds to an average of 8.2 hours of sunshine per day.

September temperatures in Princeton

Princeton average temperature in September

September rainfall

Princeton average rain in September

September hourly sunshine

Princeton average rain in September

The data used in these monthly averages covers a period of over 100 years right up until last year. As such they are a valid prediction of what to expect for the weather in Princeton in September 2025.

Other monthly averages

Best places to visit in September

UV index Best time to go?

Beta

Current (hourly) weather 15 day forecast

Princeton weather stats

Princeton weather statistics
Hottest month: July 29.3°C 84.7°F
Driest month: February 31mm 1.2ins
Sunniest month: July 10.7hrs
Coldest month: January -2.3°C 27.9°F
Wettest month: June 104mm 4.1ins
Map showing location of Princeton (41.36809, -89.46481) Princeton map pin © Google

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