Weather in September 2025

Illinois weather in September 2025

The temperatures in Illinois in September are comfortable with low of 16°C and and high up to 24°C.

You can expect about 3 to 8 days of rain in Illinois during the month of September. It’s a good idea to bring along your umbrella so that you don’t get caught in poor weather.

Our weather forecast can give you a great sense of what weather to expect in Illinois in September 2025.

If you’re planning to visit Illinois in the near future, we highly recommend that you review the 14 day weather forecast for Illinois before you arrive.

Temperatures
Temperatures
24° / 16°
Rainy Days
Rainy Days
4
Snowy Days
Snowy Days
0
Dry Days
Dry Days
26
Rainfall
Rainfall
64
mm
10.6
Sun Hours
10.6
Hrs

Illinois annual weather

Month Temperatures Rainy Days Dry Days Snowy Days Rainfall Weather More details
January -2° / -7° 5 11 15 39 mm
Awful
February 0° / -6° 4 11 14 41 mm
Awful
March 7° / 1° 6 19 6 55 mm
Bad
April 12° / 5° 7 21 3 79 mm
Awful
May 19° / 12° 7 24 0 98 mm
Ok
June 24° / 17° 7 23 0 128 mm
Good
July 27° / 20° 7 24 0 114 mm
Good
August 27° / 19° 5 26 0 100 mm
Perfect
September 24° / 16° 4 26 0 64 mm
Perfect
October 16° / 10° 5 25 0 65 mm
Good
November 9° / 3° 4 22 4 40 mm
Bad
December 3° / -2° 5 16 10 38 mm
Awful
Temperatures in Illinois in September
Rain in Illinois in September

Recommended Hotels in Illinois

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Weather in Illinois in September - FAQ

What is the average temperature in Illinois in September?
The average temperature in Illinois in September is 16/24° C.
What is the chance of rain in Illinois in September?
On average, there are 4 rainy days in Illinois during September.
Weather wise, is September a good time to visit Illinois?
The weather in Illinois in September is perfect.
Can it snow in Illinois in September?
On average, there are 0 snowy days in Illinois in September.
Cities in Illinois

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More about the weather in Illinois