October 2015 - March 2017 Illinois Divisional Average Temperature Degrees Fahrenheit -99 1901-2000 base period 1901-2000 1101 Illinois CD 1. Northwest 47.6 123 42.9 4.7 1102 Illinois CD 2. Northeast 47.8 123 43.4 4.4 1103 Illinois CD 3. West 50.1 123 46 4.1 1104 Illinois CD 4. Central 50.4 123 45.6 4.8 1105 Illinois CD 5. East 49.9 123 45.3 4.6 1106 Illinois CD 6. West Southwest 52.3 123 48.1 4.2 1107 Illinois CD 7. East Southeast 52.2 123 48.2 4.0 1108 Illinois CD 8. Southwest 54.8 123 50.7 4.1 1109 Illinois CD 9. Southeast 54.8 123 50.7 4.1