Chicago, Illinois weather in August

Averages from 2021–2025 (155 days of record).

Average high: 80°F
Average low: 66°F
Rainy days: ~10 per month
Total precipitation: 4.0 in
Warmest recorded: 99°F
Coldest recorded: 52°F

Expect August days in Chicago, Illinois to top out around 80°F and cool to about 66°F overnight, with roughly 10 days of measurable rain across the month. In recent years August has ranged from 52°F to 99°F.

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Current Chicago, Illinois forecast → · Historical data by Open-Meteo (ERA5).