| 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: | 47f - Rolling Loess Prairies |
| Heat Zone Days: | 31 - 45 days Over 86°F |
Annual Climate Data for ZIP Code 52556 - Fairfield, IA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 13 | 19 | 29 | 40 | 51 | 60 | 65 | 63 | 54 | 43 | 30 | 18 | 40 |
| Avg Max Temp (°F) | 32 | 38 | 51 | 64 | 74 | 83 | 87 | 85 | 77 | 66 | 49 | 36 | 62 |
| Avg Precip (In.) | 1.24 | 1.23 | 2.43 | 3.46 | 4.59 | 3.89 | 4.44 | 4.1 | 3.9 | 2.91 | 2.5 | 1.74 | 36.44 |