| 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 1b: -15F to -10F |
| Average First Frost Date: | Oct. 21 - Oct. 31 |
| 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: | 8 - 14 days Over 86°F |
Annual Climate Data for ZIP Code 60559 - Westmont, IL | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 14 | 19 | 28 | 38 | 48 | 58 | 63 | 62 | 54 | 42 | 31 | 20 | 40 |
| Avg Max Temp (°F) | 31 | 36 | 48 | 61 | 72 | 82 | 85 | 83 | 76 | 65 | 49 | 36 | 60 |
| Avg Precip (In.) | 1.78 | 1.57 | 2.62 | 3.76 | 3.87 | 4.08 | 3.92 | 4.37 | 3.38 | 2.67 | 3.16 | 2.46 | 37.63 |