| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F 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: | 54b - Chicago Lake Plain |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 60305 - River Forest, IL | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 14 | 19 | 29 | 38 | 48 | 58 | 64 | 63 | 54 | 42 | 32 | 21 | 40 |
| Avg Max Temp (°F) | 30 | 35 | 47 | 58 | 71 | 80 | 84 | 82 | 75 | 63 | 48 | 35 | 59 |
| Avg Precip (In.) | 1.78 | 1.6 | 2.65 | 3.72 | 3.56 | 3.95 | 3.69 | 4.42 | 3.34 | 2.67 | 3.09 | 2.46 | 36.94 |