Idaho frost dates: I
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Idaho City | Jun 17 | Sep 5 | 80 d | 6b |
| Idaho Falls | May 9 | Oct 1 | 145 d | 5b |
| Indian Valley | May 15 | Sep 27 | 135 d | 6a |
| Inkom | May 23 | Sep 24 | 124 d | 6a |
| Iona | May 9 | Oct 1 | 145 d | 5b |
| Irwin | frost any month | 6a | ||
| Island Park | frost any month | 4a | ||