Idaho Frost Dates

Average last spring and first fall frost for Idaho cities, based on 1991–2020 climate normals. Click a city for its full planting guide.

CityLast spring frostFirst fall frostSeasonZone
Boise Apr 24 Oct 21 180 days 7a
Idaho Falls May 9 Oct 1 145 days 5b
Coeur d’Alene Apr 22 Oct 18 179 days 6b

Every NOAA weather station in Idaho with complete 1991–2020 frost normals — pick the one nearest you (similar elevation matters more than plain distance).

Not sure which station to trust? Use the ZIP code lookup for the quick answer, or pick the station whose terrain most resembles your garden.

Planning a Idaho garden around these dates

Count back from the last spring frost to schedule indoor seed starting (the seed starting scheduler automates it), plant hardy crops in the weeks before the date, and hold tender crops — tomatoes, peppers, squash, basil — until after it. In fall, the first frost date is the deadline: crops must mature before it, which is what our planting calendar counts backwards for you. Crop-by-crop timing for every USDA zone lives under when to plant.