Iowa frost dates: I
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Ida Grove | Apr 27 | Oct 12 | 168 d | 5a |
| Imogene | Apr 20 | Oct 17 | 180 d | 5b |
| Independence | Apr 30 | Oct 7 | 160 d | 5a |
| Indianola | Apr 24 | Oct 12 | 171 d | 5b |
| Inwood | May 2 | Oct 2 | 153 d | 5a |
| Ionia | May 2 | Oct 5 | 156 d | 5a |
| Iowa City | Apr 21 | Oct 18 | 180 d | 5b |
| Iowa Falls | Apr 28 | Oct 10 | 165 d | 5a |
| Ira | Apr 22 | Oct 17 | 178 d | 5b |
| Ireton | May 1 | Oct 4 | 156 d | 5a |
| Irwin | Apr 27 | Oct 9 | 165 d | 5a |