Montana frost dates: A
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Absarokee | May 27 | Sep 14 | 110 d | 5a |
| Acton | May 4 | Oct 7 | 156 d | 5a |
| Alberton | May 18 | Sep 25 | 130 d | 5b |
| Alder | frost any month | 5a | ||
| Alzada | Jun 2 | Sep 6 | 96 d | 4b |
| Anaconda | Jun 1 | Sep 14 | 105 d | 5a |
| Angela | May 15 | Sep 25 | 133 d | 4a |
| Antelope | May 25 | Sep 14 | 112 d | 3b |
| Arlee | May 12 | Oct 2 | 143 d | 5b |
| Ashland | May 18 | Sep 22 | 127 d | 4b |
| Augusta | May 19 | Sep 21 | 125 d | 4b |
| Avon | Jun 9 | Sep 8 | 91 d | 4b |