My Planting Calendar

Montana frost dates

Across Montana, the average last spring frost is around May 15 and the average first fall frost around September 15 — roughly 123 frost-free days. USDA zones 3a, 3b, 4a, 4b, 5a, 5b, 6a.

Risk you acceptLast spring frost byFirst fall frost by
Cautious (~10%)May 29September 1
Average (~50%)May 15September 15
Gambler (~90%)May 1September 29

Montana spans a wide range of elevations and climates — your town’s dates can differ from the state average by two weeks or more. Look up your exact ZIP.

→ Turn these into sowing dates with the Montana planting calendar, or look up an exact ZIP code.

Statewide average from NOAA/NCEI freeze normals. Cautious/gambler dates are about two weeks either side of the average.