Weather history and climate summary information is available for the following locations:
- Belleville
- Chicago
- Moline
- Peoria
- Springfield
Warmest December Days
The warmest December days in Illinois are:
| Belleville, Illinois | 1970 | 75°F |
| Belleville, Illinois | 1948 | 75°F |
| Springfield, Illinois | 2012 | 73.9°F |
| Springfield, Illinois | 1984 | 73.9°F |
| Belleville, Illinois | 1998 | 73.4°F |
Coldest December Days
The coldest December days in Illinois were:
| Chicago, Illinois | 1983 | -25.1°F |
| Moline, Illinois | 1989 | -24.2°F |
| Peoria, Illinois | 1989 | -23.1°F |
| Springfield, Illinois | 1989 | -21.1°F |
| Moline, Illinois | 1983 | -18.9°F |
Wettest December Days
The wettest single days in December occurred:
| Springfield, Illinois | 1982 | 5.7 inches |
| Chicago, Illinois | 1982 | 3.7 inches |
| Belleville, Illinois | 2008 | 3.1 inches |
| Belleville, Illinois | 1982 | 2.6 inches |
| Belleville, Illinois | 1990 | 2.5 inches |