| 2023 Hardiness Zone: | Zone 5a: -20°F to -15°F |
| 2012 Hardiness Zone: | Zone 5a: -20°F to -15°F |
| 1990 Hardiness Zone: | Zone 4b: -25F to -20F |
| 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: | 47f - Rolling Loess Prairies |
| Heat Zone Days: | 1 - 7 days Over 86°F |
Annual Climate Data for ZIP Code 50158 - Marshalltown, IA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 7 | 13 | 25 | 37 | 49 | 59 | 63 | 60 | 50 | 39 | 26 | 14 | 37 |
| Avg Max Temp (°F) | 27 | 33 | 46 | 59 | 71 | 81 | 85 | 82 | 75 | 63 | 45 | 31 | 58 |
| Avg Precip (In.) | .94 | 1.06 | 2.35 | 3.32 | 4.29 | 5.36 | 4.48 | 4.69 | 3.45 | 2.61 | 2.16 | 1.24 | 35.97 |