Montana frost dates: H
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Hall | frost any month | 5a | ||
| Hamilton | May 21 | Sep 22 | 124 d | 5b |
| Hammond | May 17 | Sep 22 | 128 d | 4b |
| Hardin | May 13 | Sep 29 | 139 d | 4b |
| Harlem | May 16 | Sep 21 | 128 d | 4a |
| Harlowton | May 23 | Sep 16 | 116 d | 4b |
| Harrison | Apr 30 | Oct 10 | 163 d | 5a |
| Hathaway | May 8 | Sep 30 | 145 d | 4a |
| Haugan | frost any month | 6a | ||
| Havre | May 15 | Sep 23 | 131 d | 3b |
| Hays | May 18 | Sep 23 | 128 d | 4b |
| Heart Butte | Jun 8 | Sep 5 | 89 d | 4b |
| Helena | May 9 | Sep 30 | 144 d | 4b |
| Helmville | frost any month | 5a | ||
| Heron | May 20 | Sep 20 | 123 d | 6b |
| Highwood | May 7 | Oct 2 | 148 d | 4b |
| Hilger | May 14 | Sep 28 | 137 d | 4b |
| Hingham | May 24 | Sep 15 | 114 d | 4a |
| Hinsdale | May 15 | Sep 26 | 134 d | 3b |
| Hobson | May 28 | Sep 20 | 115 d | 4b |
| Hogeland | May 19 | Sep 21 | 125 d | 4a |
| Homestead | May 16 | Sep 18 | 125 d | 3b |
| Hot Springs | May 15 | Sep 28 | 136 d | 6a |
| Hungry Horse | May 9 | Oct 1 | 145 d | 5b |
| Huntley | May 12 | Sep 25 | 136 d | 4b |
| Huson | May 18 | Sep 25 | 130 d | 5b |
| Hysham | May 10 | Sep 29 | 142 d | 4b |