Idaho frost dates: C
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Calder | May 5 | Oct 2 | 150 d | 6b |
| Caldwell | Apr 23 | Oct 18 | 178 d | 7a |
| Cambridge | May 15 | Sep 27 | 135 d | 7a |
| Carey | Jun 16 | Sep 9 | 85 d | 6a |
| Careywood | May 22 | Sep 22 | 123 d | 6b |
| Carmen | May 17 | Sep 24 | 130 d | 5b |
| Cascade | frost any month | 5a | ||
| Castleford | May 17 | Sep 29 | 135 d | 6b |
| Cataldo | May 14 | Sep 26 | 135 d | 6b |
| Challis | May 14 | Sep 25 | 134 d | 5b |
| Chester | May 21 | Sep 21 | 123 d | 5a |
| Clark Fork | May 9 | Oct 8 | 152 d | 6b |
| Clarkia | May 16 | Sep 23 | 130 d | 6a |
| Clayton | May 14 | Sep 25 | 134 d | 5b |
| Clifton | May 16 | Sep 28 | 135 d | 6b |
| Cobalt | May 17 | Sep 24 | 130 d | 5b |
| Cocolalla | May 22 | Sep 22 | 123 d | 6b |
| Coeur d'Alene | Apr 22 | Oct 18 | 179 d | 6b |
| Colburn | May 8 | Sep 28 | 143 d | 6b |
| Conda | frost any month | 5a | ||
| Coolin | May 20 | Sep 13 | 116 d | 6a |
| Corral | Jun 8 | Sep 14 | 98 d | 5a |
| Cottonwood | May 6 | Oct 13 | 160 d | 6b |
| Council | May 10 | Oct 2 | 145 d | 6a |
| Craigmont | May 23 | Sep 25 | 125 d | 6b |
| Culdesac | May 23 | Sep 25 | 125 d | 7a |