| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 5b: -15°F to -10°F |
| 2012 Hardiness Zone: | Zone 5b: -15°F to -10°F |
| 1990 Hardiness Zone: | Zone 5a: -20F to -15F |
| Average First Frost Date: | Oct. 11 - Oct. 20 |
| Average Last Frost Date: | Apr. 21 - Apr. 30 |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers |
| Ecoregion: | 54f - Valparaiso-Wheaton Morainal Complex |
| Heat Zone Days: | 1 - 7 days Over 86°F |
Annual Climate Data for ZIP Code 60446 - Romeoville, IL | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 13 | 18 | 28 | 38 | 48 | 58 | 63 | 61 | 53 | 42 | 31 | 20 | 39 |
| Avg Max Temp (°F) | 30 | 36 | 48 | 61 | 72 | 82 | 85 | 83 | 76 | 65 | 49 | 36 | 60 |
| Avg Precip (In.) | 1.7 | 1.57 | 2.59 | 3.75 | 3.96 | 4.24 | 4.01 | 4.13 | 3.33 | 2.7 | 3.13 | 2.42 | 37.53 |