| 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 5a: -20F to -15F |
| Average First Frost Date: | Oct. 1 - Oct. 10 |
| Average Last Frost Date: | May 1 - May 10 |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers |
| Ecoregion: | 47b - Des Moines Lobe |
| Heat Zone Days: | 15 - 30 days Over 86°F |
Annual Climate Data for ZIP Code 50129 - Jefferson, IA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 8 | 14 | 25 | 36 | 48 | 58 | 63 | 60 | 51 | 39 | 26 | 14 | 37 |
| Avg Max Temp (°F) | 28 | 34 | 46 | 61 | 72 | 82 | 86 | 83 | 76 | 64 | 45 | 31 | 59 |
| Avg Precip (In.) | .94 | .94 | 2.16 | 3.23 | 4.19 | 4.71 | 4.13 | 3.89 | 2.98 | 2.43 | 1.92 | 1.16 | 32.69 |