| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 5b: -15°F to -10°F |
| 2012 Hardiness Zone: | Zone 5b: -15°F to -10°F |
| 1990 Hardiness Zone: | Zone 5a: -20F to -15F |
| Average First Frost Date: | Oct. 11 - Oct. 20 |
| Average Last Frost Date: | Apr. 21 - Apr. 30 |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers |
| Ecoregion: | 72d - Upper Mississippi Alluvial Plain |
| Heat Zone Days: | 15 - 30 days Over 86°F |
Annual Climate Data for ZIP Code 61523 - Chillicothe, IL | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 13 | 18 | 29 | 40 | 50 | 60 | 64 | 62 | 53 | 41 | 31 | 19 | 40 |
| Avg Max Temp (°F) | 31 | 37 | 50 | 63 | 74 | 83 | 86 | 84 | 77 | 66 | 50 | 36 | 61 |
| Avg Precip (In.) | 1.57 | 1.63 | 2.81 | 3.44 | 4.21 | 4.06 | 3.74 | 3.6 | 3.38 | 2.71 | 3.07 | 2.35 | 36.55 |