Downtown Chicago boasts a year-around average temperature of 10.8°C, peaking at 24.4°C in July, its warmest month, and dipping to an average low of -4.0°C in January, the coolest. Rainfall averages at 82.8mm annually, with May seeing the heaviest showers and February being the driest month.
Month | Temperature (Celcius) | Rainfall (mm) |
| January | -4.0 | 52.3 |
| February | -1.8 | 49.3 |
| March | 3.8 | 69.1 |
| April | 10.3 | 92.5 |
| May | 16.1 | 104.9 |
| June | 21.7 | 103.1 |
| July | 24.4 | 101.9 |
| August | 23.4 | 101.3 |
| September | 19.1 | 84.1 |
| October | 12.4 | 82.3 |
| November | 5.3 | 86.9 |
| December | -1.7 | 65.3 |