Idaho frost dates: S
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Sagle | May 8 | Sep 28 | 143 d | 6b |
| Saint Anthony | May 17 | Sep 22 | 128 d | 5a |
| Saint Charles | May 19 | Sep 21 | 125 d | 5a |
| Saint Maries | May 3 | Oct 4 | 154 d | 6b |
| Salmon | May 17 | Sep 24 | 130 d | 5b |
| Sandpoint | May 8 | Sep 28 | 143 d | 6a |
| Santa | May 3 | Oct 4 | 154 d | 6b |
| Shelley | May 23 | Sep 20 | 120 d | 5b |
| Shoshone | Apr 24 | Oct 16 | 175 d | 6a |
| Shoup | May 3 | Oct 8 | 158 d | 5b |
| Silverton | May 5 | Oct 2 | 150 d | 6b |
| Smelterville | May 14 | Sep 26 | 135 d | 6b |
| Soda Springs | frost any month | 5a | ||
| Spencer | May 18 | Sep 30 | 135 d | 5b |
| Spirit Lake | May 22 | Sep 22 | 123 d | 6b |
| Springfield | May 21 | Sep 20 | 122 d | 5b |
| Stanley | frost any month | 5b | ||
| Star | Apr 29 | Oct 13 | 167 d | 7a |
| Stites | Apr 30 | Oct 11 | 164 d | 7a |
| Sugar City | May 29 | Sep 13 | 107 d | 5a |
| Sun Valley | frost any month | 5b | ||
| Swan Valley | frost any month | 6a | ||
| Swanlake | May 31 | Sep 18 | 110 d | 5b |
| Sweet | Apr 30 | Oct 17 | 170 d | 7a |