Weather history and climate summary information is available for the following locations:
- Belleville
- Chicago
- Moline
- Peoria
- Springfield
Warmest October Days
The warmest October days in Illinois are:
| Moline, Illinois | 2006 | 95°F |
| Belleville, Illinois | 1953 | 95°F |
| Peoria, Illinois | 2006 | 93°F |
| Springfield, Illinois | 2006 | 93°F |
| Belleville, Illinois | 1952 | 93°F |
Coldest October Days
The coldest October days in Illinois were:
| Moline, Illinois | 1988 | 16°F |
| Chicago, Illinois | 1981 | 16.9°F |
| Chicago, Illinois | 1948 | 18.3°F |
| Chicago, Illinois | 1962 | 19°F |
| Chicago, Illinois | 1952 | 19.4°F |
Wettest October Days
The wettest single days in October occurred:
| Chicago, Illinois | 1989 | 4 inches |
| Chicago, Illinois | 2001 | 3.8 inches |
| Springfield, Illinois | 1973 | 3.4 inches |
| Moline, Illinois | 1998 | 3.4 inches |
| Chicago, Illinois | 1988 | 3.3 inches |