Chicago weather in September 2026

Q: How hot is it in Chicago in September?

Daytime temperatures usually reach 24°C in Chicago in September, falling to 12°C at night.

Q: How sunny is it in Chicago in September?

There are normally 8 hours of bright sunshine each day in Chicago in September - that's 61% of daylight hours.

Q: How warm is the sea around Chicago in September?

The average sea temperature around Chicago in September is 19°C.

Q: Does it rain in Chicago in September?

There are usually 9 days with some rain in Chicago in September and the average monthly rainfall is 87mm.

Expect daytime maximum temperatures of 75°F in Chicago, Illinois in September based on long-term weather averages. There are 8 hours of sunshine per day on average with typically 3.4 inches of rainfall in the month.

75
75°F max day temperature
8
8 hours of sunshine per day
9
9 days with some rainfall
54
54°F min night temperature
12
12 hours of daylight per day
0
No heat & humidity
3.4
3.4 inches of monthly rainfall
6
6 (High) UV index
66
66°F sea temperature

More about Chicago

Chicago by month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Recommended for Illinois

Air Canada: Top flight deals to the USA

Sale

Discover top Air Canada offers on flights to the USA
Browse lowest fares available or search by date
Book flights to New York, Orlando, LA, Boston & more

Go to Air Canada deal >>

View all Air Canada offers

The September weather guide for Illinois (Chicago) shows long term weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.

Metric (°C) | Imperial (°F)