Montana frost dates
Median last spring frost and first fall frost for 360 places in Montana. Last frost ranges from Apr 30 in Harrison to Jun 18 in Clancy.
Largest cities
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Billings | May 4 | Oct 7 | 156 d | 5a |
| Missoula | May 10 | Oct 1 | 144 d | 5b |
| Great Falls | May 6 | Oct 1 | 148 d | 4b |
| Bozeman | May 26 | Sep 22 | 119 d | 5a |
| Butte | Jun 13 | Sep 5 | 84 d | 4a |
| Helena | May 9 | Sep 30 | 144 d | 4b |
| Kalispell | May 31 | Sep 10 | 102 d | 5b |
| Havre | May 15 | Sep 23 | 131 d | 3b |
| Anaconda | Jun 1 | Sep 14 | 105 d | 5a |
| Miles City | May 8 | Sep 30 | 145 d | 4b |
| Belgrade | May 26 | Sep 16 | 113 d | 5a |
| Livingston | May 27 | Sep 14 | 110 d | 5a |
| Whitefish | May 16 | Sep 25 | 132 d | 5a |
| Laurel | May 5 | Oct 3 | 151 d | 5a |
| Sidney | May 11 | Sep 27 | 139 d | 4a |
| Lewistown | May 14 | Sep 28 | 137 d | 4b |
| Glendive | May 3 | Oct 4 | 154 d | 4a |
| Columbia Falls | May 31 | Sep 10 | 102 d | 5a |
| Polson | May 10 | Oct 5 | 148 d | 6a |
| Hamilton | May 21 | Sep 22 | 124 d | 5b |
| Bigfork | May 12 | Sep 25 | 136 d | 5b |
| Dillon | Jun 5 | Sep 13 | 100 d | 5a |
| Lolo | May 16 | Sep 26 | 133 d | 5b |
| Hardin | May 13 | Sep 29 | 139 d | 4b |
| Glasgow | May 6 | Sep 30 | 147 d | 4a |
| Shelby | May 23 | Sep 16 | 116 d | 4a |
| Cut Bank | May 24 | Sep 15 | 114 d | 4a |
| Warm Springs | Jun 1 | Sep 14 | 105 d | 4b |
| Deer Lodge | frost any month | 4b | ||
| Wolf Point | May 8 | Sep 28 | 143 d | 4a |
| Lakeside | May 12 | Sep 25 | 136 d | 6a |
| Libby | May 10 | Sep 26 | 139 d | 6a |
| Conrad | May 20 | Sep 19 | 122 d | 4a |
| Colstrip | May 15 | Sep 30 | 138 d | 5a |
| Big Sky | frost any month | 4b | ||
| Pablo | May 10 | Oct 5 | 148 d | 6a |
| Red Lodge | Jun 3 | Sep 19 | 108 d | 5a |
| East Helena | May 9 | Sep 30 | 144 d | 5a |
| Lame Deer | May 23 | Sep 15 | 115 d | 5a |
| Columbus | May 27 | Sep 14 | 110 d | 5a |