Weather in Chicago in September 2025
Average weather
Average temperature in Chicago in September
The expected average maximum temperature in September is +24°C with a maximum of +34°C and a minimum of +12°C.
The average maximum temperature goes down 5% by the end of the month, compared with the beginning of the month, from +28°C to +27°C.
Is Chicago warm or cold in September?
Chicago is typically warm in September.
Maximum temperatures go down compared to the previous month from +27°C to +23°C. The minimum temperature also goes down from +20°C to +16°C.
It’s generally warm, but pack a long-sleeve shirt for evenings.
Take a look at how September is compared to other months in Chicago:
Water temperature in Chicago in September
Water in Chicago in September is Fresh. It varies from +18°C to +23°C, with an average of +20°C. This is almost similar to the air temperature, which averages +23°C.
The water temperature in September is one of the warmest of the entire year:
Can you swim in Chicago in September?
Climate in Chicago in September
| August | September | October | ||||
|---|---|---|---|---|---|---|
| Avg. temperature | ||||||
| +27°C | +23°C | +16°C | ||||
| Min. temperature | ||||||
| +11°C | +5°C | -2°C | ||||
| Max. temperature | ||||||
| +38°C | +36°C | +31°C | ||||
| Rainfall | ||||||
| 90 mm | 75 mm | 81 mm | ||||
| Wind | ||||||
| 3 m/s | 3 m/s | 4 m/s | ||||
| Avg. water temperature | ||||||
| +23°C | +20°C | +15°C | ||||
| Humidity | ||||||
| 69% | 67% | 67% | ||||
| Air pressure | ||||||
| 1015 HPa | 1016 HPa | 1016 HPa | ||||
| Sunny days | ||||||
| 5 | 7 | 6 | ||||
| Cloudy days | ||||||
| 10 | 9 | 11 | ||||
| Rainy days | ||||||
| 12 | 11 | 12 | ||||
| Snowy days | ||||||
| 0 | 0 | 0 | ||||
September weather is still as good as in August. It’s getting colder in September. From +27°C in the day, the average maximum temperature lowers to +23°C. As September arrives, the amount of rainfall goes down. On average, the rainfall volume decreases from 90 mm to 75 mm. It feels drier, as humidity decreases from 69% to 67%. The average wind speed doesn’t change much during September, staying around 3 m/s. The good news is there are likely to be more sunny days in September, from 5 to 7.
October brings much the same weather, it remains good.
Wind
The average wind speed is 3 m/s getting up to 6 m/s which is a medium breeze. You can feel it, especially getting out of the water.
The average wind speed in Chicago is gradually increasing during September, going from 3 m/s to 3 m/s over the course of the month.
Rain
How was the weather last September in Chicago?
Climate Change over Years
The climate in Chicago in September has not changed much over the last 43 years.
The average temperature was the lowest in 1979 (+12°C) and the highest in 2012 (+17°C). The driest year was 2005 with only 501 mm of rainfall, and the wettest year was 2023 with 1535 mm.
FAQ
Is September a good time to visit Chicago?
Can you sunbathe in Chicago in September?
Can you swim in Chicago in September?
Is Chicago rainy in September?
Is it sunny in Chicago in September?
Other cities in USA
Monthly weather in Chicago
Source of the data
For this page, we’ve looked at the typical weather in Chicago, based on historical hourly weather data from January 1, 1979, to December 31, 2023.
For past dates, we show actual recorded data at the location at that time. Forecasts are based on recorded weather during that day of the year, averaged over the total years for which we have records (unless stated otherwise). The daily temperature is the highest recorded temperature in the shadow during that day.