| 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 1b: -15F to -10F |
| 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: | 72f - River Hills |
| Heat Zone Days: | 61 - 90 days Over 86°F |
Annual Climate Data for ZIP Code 63021 - Ballwin, MO | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 19 | 23 | 33 | 44 | 53 | 62 | 67 | 65 | 56 | 45 | 34 | 24 | 44 |
| Avg Max Temp (°F) | 38 | 44 | 55 | 66 | 76 | 84 | 89 | 87 | 80 | 69 | 55 | 42 | 65 |
| Avg Precip (In.) | 2.3 | 2.36 | 3.79 | 4.05 | 4.34 | 3.88 | 3.83 | 3.45 | 3.24 | 3.01 | 4.15 | 3.08 | 41.48 |