Average annual temperature is 13.1 °C
Absolute maximum temperature: 36.3 °C
Absolute minimum temperature: -13.9 °C
Number of sunny days: 198 days
Number of rainy days: 156 days
Number of snow days: 11 days
Look at detailed online map of Illinois
* Weather data for Illinois United States is based on climate observations for 2026 year
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Absolute maximum temperature (°C) | 18.9 | 17.0 | 22.0 | 27.6 | 31.1 | 33.6 | 34.5 | 36.3 | 31.8 | 29.2 | 24.6 | 16.3 |
| Average daytime temperature (°C) | 6.1 | 9.0 | 10.9 | 19.2 | 25.3 | 29.2 | 29.0 | 28.0 | 26.0 | 19.0 | 12.3 | 8.5 |
| Average temperature (°C) | 1.5 | 2.9 | 5.1 | 12.0 | 18.8 | 23.0 | 24.0 | 23.1 | 20.5 | 14.0 | 6.7 | 4.4 |
| Average night temperature (°C) | -1.7 | -1.5 | 0.7 | 6.2 | 12.6 | 16.9 | 19.2 | 18.9 | 15.8 | 9.9 | 2.2 | 1.6 |
| Absolute minimum temperature (°C) | -13.7 | -13.9 | -10.0 | -1.8 | 3.6 | 11.2 | 15.5 | 11.9 | 10.2 | -2.2 | -9.2 | -7.6 |
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight maximum duration (h) | 10.0 | 11.0 | 12.0 | 13.0 | 14.0 | 15.0 | 14.0 | 14.0 | 13.0 | 11.0 | 10.0 | 9.0 |
| Daylight mean duration (h) | 9.7 | 10.7 | 12.0 | 13.3 | 14.4 | 15.0 | 14.7 | 13.7 | 12.5 | 11.1 | 10.0 | 9.4 |
| Daylight minimum duration (h) | 9.0 | 10.0 | 11.0 | 12.0 | 13.0 | 14.0 | 14.0 | 13.0 | 11.0 | 10.0 | 9.0 | 9.0 |
| Sunshine mean duration (h) | 4.2 | 7.4 | 6.6 | 9.8 | 11.1 | 12.8 | 12.6 | 10.5 | 10.1 | 7.6 | 7.7 | 4.8 |
| Precipitation (mm) | 50 | 82 | 109 | 62 | 25 | 43 | 110 | 127 | 87 | 79 | 21 | 68 |
| Sunny days | 13 | 16 | 12 | 19 | 18 | 21 | 12 | 11 | 19 | 18 | 22 | 17 |
| Rainy days | 11 | 10 | 18 | 11 | 13 | 9 | 19 | 20 | 11 | 13 | 7 | 14 |
| Snow days | 7 | 2 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 |
The best time to visit Illinois during the most sunny months:
The largest precipitation sum in Illinois is at