Weather history and climate summary information is available for the following locations:
- Belleville
- Chicago
- Moline
- Peoria
- Springfield
Warmest August Days
The warmest August days in Illinois are:
| Belleville, Illinois | 2007 | 104.5°F |
| Belleville, Illinois | 1964 | 104°F |
| Peoria, Illinois | 1988 | 102.9°F |
| Moline, Illinois | 1987 | 102.9°F |
| Belleville, Illinois | 1962 | 102.9°F |
Coldest August Days
The coldest August days in Illinois were:
| Moline, Illinois | 1986 | 39.9°F |
| Chicago, Illinois | 1965 | 41°F |
| Peoria, Illinois | 1986 | 41°F |
| Chicago, Illinois | 1964 | 41°F |
| Chicago, Illinois | 1963 | 42.1°F |
Wettest August Days
The wettest single days in August occurred:
| Chicago, Illinois | 1987 | 9.2 inches |
| Peoria, Illinois | 1982 | 7 inches |
| Moline, Illinois | 1987 | 4.6 inches |
| Springfield, Illinois | 1981 | 4.4 inches |
| Chicago, Illinois | 2001 | 4.3 inches |