Montana frost dates: W
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Warm Springs | Jun 1 | Sep 14 | 105 d | 4b |
| West Glacier | May 18 | Sep 20 | 125 d | 5a |
| West Yellowstone | frost any month | 4b | ||
| Westby | May 18 | Sep 21 | 126 d | 3b |
| White Sulphur Springs | Jun 4 | Sep 11 | 99 d | 4b |
| Whitefish | May 16 | Sep 25 | 132 d | 5a |
| Whitehall | Jun 13 | Sep 5 | 84 d | 5a |
| Whitetail | May 28 | Sep 7 | 102 d | 3b |
| Whitewater | May 19 | Sep 22 | 126 d | 3b |
| Whitlash | frost any month | 4a | ||
| Wibaux | May 27 | Sep 16 | 112 d | 4a |
| Willard | May 12 | Sep 26 | 137 d | 4b |
| Willow Creek | May 26 | Sep 15 | 112 d | 5a |
| Wilsall | Jun 4 | Sep 6 | 94 d | 4b |
| Winifred | May 16 | Sep 23 | 130 d | 4b |
| Winnett | May 16 | Sep 28 | 135 d | 4b |
| Winston | May 19 | Sep 19 | 123 d | 5a |
| Wisdom | frost any month | 5a | ||
| Wise River | frost any month | 5a | ||
| Wolf Creek | May 19 | Sep 24 | 128 d | 4b |
| Wolf Point | May 8 | Sep 28 | 143 d | 4a |
| Worden | May 12 | Sep 25 | 136 d | 4b |
| Wyola | May 21 | Sep 17 | 119 d | 4b |