| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 7a: 0°F to 5°F |
| 2012 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 7a: 0°F to 5°F |
| 1990 Hardiness Zone: | Zone 6b: -5F to 0F |
| Average First Frost Date: | Oct. 21 - Oct. 31 |
| Average Last Frost Date: | Apr. 21 - Apr. 30 |
| Koppen-Geiger Climate Zone: | Cfa - Humid Subtropical Climate |
| Ecoregion: | 39d - Central Plateau |
| Heat Zone Days: | 61 - 90 days Over 86°F |
Annual Climate Data for ZIP Code 65606 - Alton, MO | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 19 | 23 | 33 | 41 | 51 | 60 | 65 | 63 | 54 | 42 | 32 | 24 | 42 |
| Avg Max Temp (°F) | 43 | 50 | 59 | 69 | 77 | 85 | 90 | 89 | 81 | 72 | 57 | 46 | 68 |
| Avg Precip (In.) | 2.76 | 2.99 | 4.34 | 4.29 | 4.68 | 3.65 | 3.35 | 3.08 | 3.64 | 3.47 | 5.1 | 4.17 | 45.51 |