| City | Population | Last spring frost | First fall frost | Growing season | Zone |
|---|---|---|---|---|---|
| Billings | 121,239 | May 4 | Oct 7 | 156 days | 5a |
| Missoula | 78,903 | May 10 | Oct 1 | 143 days | 5b |
| Great Falls | 60,208 | May 6 | Oct 1 | 147 days | 4b |
| Bozeman | 58,814 | May 26 | Sep 22 | 116 days | 5a |
| Butte | 35,469 | Jun 13 | Sep 5 | 83 days | 5a |
| Helena | 35,138 | May 9 | Sep 30 | 142 days | 5a |
| Kalispell | 31,851 | May 31 | Sep 10 | 100 days | 5b |
| Belgrade | 13,107 | May 26 | Sep 16 | 112 days | 5a |
| Anaconda | 9,709 | Jun 1 | Sep 14 | 105 days | 5a |
| Whitefish | 9,358 | May 16 | Sep 25 | 129 days | 5a |
| Livingston | 9,290 | May 27 | Sep 14 | 108 days | 5a |
| Havre | 9,264 | May 15 | Sep 23 | 129 days | 3b |
| Miles City | 8,450 | May 8 | Sep 30 | 144 days | 4b |
| Laurel | 7,205 | May 5 | Oct 3 | 149 days | 5a |
| Sidney | 6,217 | May 11 | Sep 27 | 137 days | 4a |
| Lewistown | 6,179 | May 23 | Sep 21 | 119 days | 4b |
| Columbia Falls | 5,753 | May 31 | Sep 10 | 100 days | 5a |
| Polson | 5,653 | May 10 | Oct 5 | 147 days | 6a |
| Hamilton | 5,451 | May 21 | Sep 22 | 122 days | 5b |