Montana planting zones & frost dates

Last updated October 19, 2026

The 2 Montana cities on this site fall in zones 5a, 5b. Last spring frost dates range from May 11 in Billings to May 22 in Missoula.

City	Zone	Last frost	First frost	Population
Billings	5a	May 11	Sep 28	121,483
Missoula	5b	May 22	Sep 20	78,204

Frost dates are 30%-risk dates from the nearest suitable NOAA station. Population: Census Vintage 2024 estimates.