Frost dates by state › Idaho
Idaho frost dates
Average last spring and first fall frost dates for Idaho’s largest cities, with each city’s USDA hardiness zone.
Reviewed October 2026
Among Idaho’s 20 largest cities, the average last spring frost ranges from Apr 6 in Lewiston to May 16 in Chubbuck. Elevation, distance from the coast and city heat all shift the date, so use your own ZIP code below for the closest match.
In Moscow, the nearest weather station can record a freeze in any month, so pick fast, cold-tolerant crops and keep covers ready.
| City | Average last spring frost | Average first fall frost | Frost-free days | Hardiness zone | Weather station used |
|---|---|---|---|---|---|
| Boise City | Apr 24 | Oct 21 | 180 | 7a | Boise Air Terminal, ID, 2 mi |
| Meridian | Apr 24 | Oct 21 | 180 | 7a | Boise Air Terminal, ID, 9 mi |
| Nampa | Apr 29 | Oct 13 | 167 | 7a | Nampa Sugar Factory, ID |
| Caldwell | Apr 29 | Oct 13 | 167 | 7a | Nampa Sugar Factory, ID, 5 mi |
| Idaho Falls | May 9 | Oct 1 | 145 | 5b | Idaho Falls - Kifi, ID, 2 mi |
| Pocatello | May 2 | Oct 11 | 162 | 6a–6b | Pocatello City, ID |
| Coeur d'Alene | Apr 22 | Oct 18 | 179 | 6b | Coeur D'Alene, ID |
| Twin Falls | Apr 30 | Oct 9 | 162 | 7a | Twin Falls-Kmvt, ID |
| Post Falls | Apr 22 | Oct 18 | 179 | 6b | Coeur D'Alene, ID, 7 mi |
| Rexburg | May 12 | Sep 24 | 135 | 5a | Rexburg Byu Idaho, ID |
| Lewiston | Apr 6 | Oct 26 | 203 | 7a | Lewiston Nez Perce Co Airport, ID, 2 mi |
| Eagle | Apr 30 | Oct 17 | 170 | 7a | Emmett 2 E, ID, 6 mi |
| Kuna | Apr 24 | Oct 21 | 180 | 7a | Boise Air Terminal, ID, 9 mi |
| Moscow | Any month | Any month | – | 6b | Moscow U Of I, ID, 2 mi |
| Ammon | May 9 | Oct 1 | 145 | 5b | Idaho Falls - Kifi, ID, 4 mi |
| Star | Apr 29 | Oct 13 | 167 | 7a | Nampa Sugar Factory, ID, 8 mi |
| Hayden | Apr 22 | Oct 18 | 179 | 6b | Coeur D'Alene, ID, 6 mi |
| Mountain Home | May 2 | Oct 8 | 159 | 7a | Mtn Home, ID |
| Chubbuck | May 16 | Oct 2 | 139 | 6a–6b | Pocatello 2 Ne, ID, 4 mi |
| Jerome | May 2 | Oct 14 | 165 | 6b | Jerome, ID |
Frost dates are the dates after (spring) or before (fall) which the chance of a 32°F freeze is below 50%, from NOAA’s 1991–2020 U.S. Climate Normals for the weather station nearest each city’s center. Zones are from the 2023 USDA Plant Hardiness Zone Map for the ZIP codes around each city; a range means nearby ZIP codes differ. Cities are the 20 largest by Census Bureau 2024 population estimates.
An average is not a guarantee. There’s still about a 1 in 2 chance of frost after the average last spring date. Many gardeners wait an extra week or two before setting out tomatoes, peppers and basil, and keep covers handy.
Planting dates for Boise City
Timed from Boise City’s average last frost of Apr 24, using University of New Hampshire Extension’s planting guidance. For your exact dates, enter your ZIP code in the calendar below.
| Crop | Start seeds indoors | Plant outside |
|---|---|---|
| Tomatoes | Mar 6 to Mar 20 | May 1 to May 8 |
| Peppers | Feb 27 to Mar 13 | May 8 |
| Lettuce | Feb 20 to Feb 27 | Mar 27 to Apr 3 |
| Broccoli | Feb 13 to Feb 27 | Mar 27 to Apr 10 |
| Cucumbers | Apr 3 to Apr 10 | May 1 to May 8 |
| Basil | Mar 13 to Mar 27 | May 8 |
When to plant, for your garden
Your seed-starting and planting dates, timed from your last spring frost. Full calendar, 12 crops.
Enter your ZIP code to look up your average last frost date and hardiness zone, or type the date in yourself.
Frost dates: NOAA U.S. Climate Normals, 1991–2020. Hardiness zones: USDA Plant Hardiness Zone Map, 2023, ZIP code data from PRISM Group, Oregon State University, prism.oregonstate.edu, accessed Oct. 20, 2026.
More about frost dates
How to find your last frost date, and what your zone means · Full planting calendar · How to start seeds indoors
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