| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 7a: 0°F to 5°F |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 6b: -5°F to 0°F |
| 1990 Hardiness Zone: | Zone 6a: -10F to -5F |
| Average First Frost Date: | Nov. 1 - Nov. 10 |
| Average Last Frost Date: | Apr. 11 - Apr. 20 |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers |
| Ecoregion: | 72e - Middle Mississippi Alluvial Plain |
| Heat Zone Days: | 46 - 60 days Over 86°F |
Annual Climate Data for ZIP Code 62002 - Alton, IL | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 19 | 24 | 34 | 45 | 55 | 64 | 69 | 66 | 58 | 46 | 35 | 24 | 45 |
| Avg Max Temp (°F) | 36 | 42 | 52 | 64 | 75 | 84 | 88 | 86 | 79 | 68 | 53 | 41 | 64 |
| Avg Precip (In.) | 2.06 | 2.23 | 3.49 | 4.03 | 4.28 | 3.29 | 3.62 | 3.26 | 3.12 | 2.76 | 3.79 | 2.93 | 38.86 |