Montana frost dates: F
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Fairfield | May 13 | Sep 27 | 137 d | 4b |
| Fairview | May 11 | Sep 27 | 139 d | 4a |
| Fallon | May 20 | Sep 22 | 125 d | 4a |
| Fishtail | Jun 1 | Sep 11 | 102 d | 5a |
| Flaxville | May 28 | Sep 7 | 102 d | 4a |
| Florence | May 22 | Sep 19 | 120 d | 5b |
| Floweree | May 23 | Sep 23 | 123 d | 4b |
| Forest Grove | May 19 | Sep 25 | 129 d | 4b |
| Forsyth | May 9 | Sep 29 | 143 d | 4b |
| Fort Benton | May 20 | Sep 19 | 122 d | 4a |
| Fort Harrison | May 9 | Sep 30 | 144 d | 4b |
| Fort Peck | May 8 | Oct 1 | 146 d | 4a |
| Fort Shaw | Jun 2 | Sep 10 | 100 d | 4b |
| Fort Smith | May 7 | Oct 5 | 151 d | 5a |
| Fortine | May 16 | Sep 18 | 125 d | 5a |
| Frazer | May 12 | Sep 24 | 135 d | 4a |
| Frenchtown | May 18 | Sep 25 | 130 d | 6a |
| Froid | May 16 | Sep 18 | 125 d | 4a |
| Fromberg | May 14 | Sep 24 | 133 d | 5a |