| 2023 Hardiness Zone: | Zone 5a: -20°F to -15°F Zone 5b: -15°F to -10°F |
| 2012 Hardiness Zone: | Zone 5a: -20°F to -15°F |
| 1990 Hardiness Zone: | Zone 4b: -25F to -20F |
| Average First Frost Date: | Oct. 11 - Oct. 20 |
| Average Last Frost Date: | May 1 - May 10 |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers |
| Ecoregion: | 47f - Rolling Loess Prairies |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 50112 - Grinnell, IA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 8 | 13 | 24 | 35 | 46 | 56 | 61 | 59 | 49 | 37 | 25 | 14 | 36 |
| Avg Max Temp (°F) | 27 | 33 | 46 | 59 | 70 | 80 | 84 | 82 | 75 | 63 | 46 | 32 | 58 |
| Avg Precip (In.) | 1.16 | 1.22 | 2.34 | 3.53 | 4.34 | 4.7 | 4.17 | 4.42 | 3.59 | 2.7 | 2.4 | 1.44 | 36.01 |