Boise, Idaho: freeze dates & growing season

Three different things get called “Boise” here, so this page is explicit about all three: the metro label (Boise), the anchor geography (Census ZCTA 83702, a downtown ZIP-code area), and the climate record (the NOAA station below). Windows are calculated from the station — not from your street address.

Climate basis: NOAA station Boise 7 N, ID (USC00101017), 6 mi (9 km) from the ZCTA 83702 centroid, elevation 3885 ft, on the 1991–2020 climate normals.

Last spring freezeMay 171-in-10 after Jun 10

First fall freezeOctober 121-in-10 before Sep 27

Frost-free season≈ 147 daysmedian at 32°F

Hard freeze, 28°Apr 27 – Oct 24kills even hardy greens

USDA zone7a0 to 5°F winter low — not frost timing

The year

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to Jun 10

The Boise year: hatched areas are the freeze-likely seasons in 1991–2020 normals.

What that means in practice

Tomatoes: plant May 24 – June 7
Peas: plant April 5 – April 19
Garlic: plant cloves October 19 – October 26

All 79 crops in Boise

These windows describe typical years (1991–2020 climate normals), not this year's forecast. Freezes happen outside them — especially in frost pockets, valleys, and urban edges. Watch the forecast before committing tender plants.

Check a specific ZIP instead

Metro climates vary — elevation, water, and urban heat shift freeze dates by days to weeks. Look up your exact ZIP:

Nearby reviewed metros

Spokane, WA · Salt Lake City, UT · Reno, NV · Portland, OR · Seattle, WA