| 2023 Hardiness Zone: | Zone 5b: -15°F to -10°F | |
| 2012 Hardiness Zone: | Zone 5a: -20°F to -15°F 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: | 47b - Des Moines Lobe | |
| Current Drought Status: | Exceptional Drought | |
| Heat Zone Days: | 1 - 7 days Over 86°F |
Annual Climate Data for ZIP Code 50131 - Johnston, IA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 10 | 16 | 27 | 38 | 50 | 60 | 65 | 62 | 52 | 41 | 28 | 16 | 39 |
| Avg Max Temp (°F) | 28 | 35 | 47 | 60 | 72 | 81 | 85 | 83 | 75 | 64 | 46 | 33 | 59 |
| Avg Precip (In.) | .84 | 1.01 | 2.16 | 3.35 | 4.34 | 4.89 | 4.23 | 4.19 | 3.16 | 2.54 | 2.03 | 1.12 | 33.87 |