Idaho frost dates: B
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Bancroft | May 21 | Sep 21 | 123 d | 5a |
| Banks | Jun 1 | Sep 10 | 101 d | 7a |
| Basalt | May 5 | Oct 3 | 151 d | 5b |
| Bayview | May 22 | Sep 22 | 123 d | 6b |
| Bellevue | May 13 | Oct 2 | 142 d | 5b |
| Bern | Jun 17 | Sep 3 | 78 d | 5a |
| Blackfoot | May 5 | Oct 3 | 151 d | 5b |
| Blanchard | May 12 | Sep 21 | 132 d | 6b |
| Bliss | May 3 | Oct 1 | 151 d | 7a |
| Bloomington | May 19 | Sep 21 | 125 d | 5a |
| Boise | Apr 24 | Oct 21 | 180 d | 7a |
| Bonners Ferry | Apr 30 | Oct 4 | 157 d | 6a |
| Bovill | May 16 | Sep 23 | 130 d | 6a |
| Bruneau | Apr 17 | Oct 17 | 183 d | 7a |
| Buhl | Apr 25 | Oct 15 | 173 d | 7a |
| Burley | May 7 | Oct 4 | 150 d | 6b |