| 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. 11 - Oct. 20 |
| 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: | 31 - 45 days Over 86°F |
Annual Climate Data for ZIP Code 62959 - Marion, IL | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 20 | 23 | 33 | 43 | 52 | 61 | 66 | 63 | 55 | 43 | 34 | 24 | 43 |
| Avg Max Temp (°F) | 39 | 45 | 55 | 66 | 75 | 84 | 88 | 86 | 80 | 69 | 55 | 43 | 65 |
| Avg Precip (In.) | 3.19 | 3.13 | 4.44 | 4.49 | 4.84 | 4.29 | 3.84 | 3.64 | 3.11 | 3.06 | 4.65 | 3.74 | 46.43 |