Frost Dates & Planting Calendars in Montana
Typical last spring frost, first fall frost, and growing-season length for 20 cities in Montana, based on NOAA 1991–2020 climate normals. Click a city for its full frost-date summary, monthly temperature chart, and 42-crop planting calendar.
| City | Last Spring Frost (typical) | First Fall Frost (typical) | Growing Season | USDA Zone |
|---|---|---|---|---|
| Billings | May 10 | October 1 | 142 days | 5a |
| Missoula | May 10 | October 1 | 143 days | 5b |
| Great Falls | May 6 | October 1 | 147 days | 4b |
| Bozeman | May 26 | September 22 | 116 days | 5a |
| Butte | June 13 | September 5 | 83 days | 5a |
| Helena | May 9 | September 30 | 142 days | 5a |
| Kalispell | May 31 | September 10 | 100 days | 5b |
| Havre | May 15 | September 23 | 129 days | 3b |
| Anaconda | June 1 | September 14 | 105 days | 5a |
| Miles City | May 8 | September 30 | 144 days | 4b |
| Helena Valley Southeast | May 9 | September 30 | 142 days | 5a |
| Belgrade | May 26 | September 16 | 112 days | 5a |
| Helena Valley West Central | May 9 | September 30 | 142 days | 4b |
| Evergreen | May 31 | September 10 | 100 days | 5b |
| Livingston | May 27 | September 14 | 108 days | 5a |
| Whitefish | May 16 | September 25 | 129 days | 5a |
| Laurel | May 5 | October 3 | 149 days | 5a |
| Sidney | May 11 | September 27 | 137 days | 4a |
| Lockwood | May 10 | October 1 | 142 days | 5a |
| Lewistown | May 14 | September 28 | 135 days | 4b |