The temperatures in Illinois in August are comfortable with low of 66°F and and high up to 80°F.
You can expect about 3 to 8 days of rain in Illinois during the month of August. 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 August 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
80° / 66°
Rainy Days
5
Snowy Days
0
Dry Days
26
Rainfall
3.94
in
Sun Hours
11.1
Hrs
