Montana planting zones & frost dates
USDA hardiness zones in Montana go from 4b to 5b. Pick your city for its average frost dates and a planting calendar, or search by ZIP code.
| City | Zone | Avg. last frost | Avg. first frost |
|---|---|---|---|
| Billings | 5a | May 10 | Oct 1 |
| Bozeman | 5a | May 26 | Sep 22 |
| Butte | 4b | Jun 13 | Sep 5 |
| Great Falls | 4b | May 6 | Oct 1 |
| Helena | 5a | May 9 | Sep 30 |
| Kalispell | 5b | May 31 | Sep 10 |
| Missoula | 5b | May 10 | Oct 1 |
Cities with 10,000+ residents. Data: USDA Plant Hardiness Zone Map 2023 and NOAA Climate Normals 1991–2020. Sources and method.