Idaho Falls, ID Frost Dates & Growing Season

The two dates every Idaho Falls garden is planned around, plus ready-computed planting windows for the most popular crops.

Last spring frost
May 9
~50% chance of frost after
First fall frost
Oct 1
~50% chance of frost before
Growing season
145 days
frost-free stretch
USDA zone
5b
2023 hardiness map
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost Apr 27 May 9 Jun 2
First fall frost Oct 15 Oct 1 Sep 17
Hard freeze (28°F), median last Apr 28 · first Oct 13

Computed from NOAA 1991–2020 climate normals at the Idaho Falls - Kifi station (3 km from central Idaho Falls). "Safe" means frost past that date happens only about one year in ten. Your exact garden can still run days either way with elevation and terrain — check your own ZIP with the frost date lookup.

Planting windows for Idaho Falls

Computed from Idaho Falls's own frost dates. Click any crop for the full zone-5 growing guide — varieties, spacing, fall plantings, and more.

CropStart seeds indoorsTransplantDirect sow
🍅 Tomatoes Mar 14 – Mar 28 May 16 – May 23
🫑 Peppers Feb 28 – Mar 14 May 23 – May 30
🥬 Lettuce Mar 28 – Apr 11 Apr 11 – Apr 25 Apr 11 – May 9
🫛 Peas Mar 28 – Apr 11
🥕 Carrots Apr 18 – May 9
🥦 Broccoli Mar 21 – Apr 4 Apr 18 – May 2
🥬 Kale Mar 28 – Apr 11 Apr 11 – Apr 25 Apr 11 – Apr 25
🥒 Cucumbers Apr 11 – Apr 18 May 16 – May 23 May 16 – May 23
🥒 Zucchini Apr 11 – Apr 18 May 16 – May 23 May 16 – May 23
🫘 Green Beans (Bush) May 16 – May 23
🌽 Sweet Corn May 16 – May 23
🌿 Basil Mar 28 – Apr 11 May 16 – May 23 May 23 – May 30
🧄 Garlic Fall: Aug 20 – Sep 17

Want this for all 50 crops, or as a printable seed-shelf schedule? Use the planting calendar and the seed starting scheduler — both can use Idaho Falls's dates automatically after a lookup.

Reading the season in Idaho Falls

At about 145 frost-free days, Idaho Falls rewards efficiency: start warm-season crops indoors, favor short-season varieties, and lean on cold-tolerant crops — peas, kale, roots — that shrug off the shoulder-season frosts on either end.

Frequently asked questions

When is the last frost in Idaho Falls, ID?

The average last spring frost in Idaho Falls is around May 9, based on 1991–2020 climate normals. That's a median — about half of years see a later frost, so tender crops are safest going out a week or two after this date.

When is the first frost in Idaho Falls, ID?

The average first fall frost in Idaho Falls arrives around Oct 1. Crops still in the garden need to mature before then, and frost-tender plants need harvesting or protection as the date approaches.

How long is the growing season in Idaho Falls?

About 145 frost-free days on average, from May 9 to Oct 1. That favors short-season varieties and transplants for warm-season crops, with cool-season vegetables doing the heavy lifting in spring and fall.

What USDA zone is Idaho Falls in?

USDA zone 5b on the 2023 Plant Hardiness Zone Map. Note that zones describe winter cold, not frost timing — these frost dates are the numbers to plan plantings around.