| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F |
| 1990 Hardiness Zone: | Zone 1b: -15F to -10F |
| Average First Frost Date: | Oct. 11 - Oct. 20 |
| Average Last Frost Date: | Apr. 11 - Apr. 20 |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers |
| Ecoregion: | 72d - Upper Mississippi Alluvial Plain |
| Heat Zone Days: | 61 - 90 days Over 86°F |
Annual Climate Data for ZIP Code 62037 - Grafton, IL | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 19 | 23 | 33 | 43 | 54 | 63 | 67 | 65 | 56 | 45 | 35 | 24 | 44 |
| Avg Max Temp (°F) | 37 | 43 | 54 | 66 | 75 | 84 | 89 | 87 | 80 | 68 | 54 | 41 | 65 |
| Avg Precip (In.) | 2.01 | 1.97 | 3.45 | 4 | 4.1 | 3.5 | 3.71 | 3.27 | 3.11 | 2.66 | 3.74 | 2.88 | 38.4 |