My Planting Calendar

Idaho frost dates

Across Idaho, the average last spring frost is around May 10 and the average first fall frost around September 25 — roughly 138 frost-free days. USDA zones 3b, 4b, 5b, 6a, 6b, 7a.

Risk you acceptLast spring frost byFirst fall frost by
Cautious (~10%)May 24September 11
Average (~50%)May 10September 25
Gambler (~90%)April 26October 9

Idaho 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 Idaho 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.