| 2023 Hardiness Zone: | Zone 7a: 0°F to 5°F |
| 2012 Hardiness Zone: | Zone 6b: -5°F to 0°F |
| 1990 Hardiness Zone: | Zone 6a: -10F to -5F |
| Average First Frost Date: | Oct. 21 - Oct. 31 |
| Average Last Frost Date: | Apr. 11 - Apr. 20 |
| Koppen-Geiger Climate Zone: | Cfa - Humid Subtropical Climate |
| Ecoregion: | 72j - Southern Illinoian Till Plain |
| Heat Zone Days: | 61 - 90 days Over 86°F |
Annual Climate Data for ZIP Code 62260 - Millstadt, IL | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 21 | 25 | 35 | 45 | 54 | 64 | 68 | 66 | 58 | 46 | 36 | 26 | 45 |
| Avg Max Temp (°F) | 38 | 44 | 55 | 67 | 76 | 85 | 89 | 87 | 80 | 69 | 55 | 43 | 66 |
| Avg Precip (In.) | 2.22 | 2.34 | 3.68 | 3.98 | 4.19 | 3.9 | 3.84 | 3.26 | 3.23 | 2.97 | 4.08 | 3.16 | 40.84 |