Idaho Planting Guide & Growing Season
Idaho is in USDA hardiness zone 3b-7a with a growing season of 135 days. The average last spring frost is May 15 and the average first fall frost is Sep 25. Climate data based on Boise.
Growing Conditions in Idaho
How Idaho Compares
Compare Idaho's growing conditions with states that have similar climates.
| State | USDA Zone | Last Frost | First Frost | Season (days) |
|---|---|---|---|---|
| Idaho (ID) | 3b-7a | May 15 | Sep 25 | 135 |
| Alabama (AL) | 7a-8b | Mar 15 | Nov 5 | 235 |
| Alaska (AK) | 1a-7b | May 30 | Sep 5 | 100 |
| Arizona (AZ) | 4b-10b | Mar 1 | Nov 15 | 260 |
| Arkansas (AR) | 6b-8a | Apr 1 | Oct 25 | 210 |
| California (CA) | 4b-11a | Feb 15 | Nov 30 | 290 |
Frequently Asked Questions About Gardening in Idaho
When should I start seeds indoors in Idaho?
In Idaho, the average last frost date is May 15. Start most seeds indoors 6-8 weeks before this date. The USDA hardiness zone for Idaho is 3b-7a, with a growing season of approximately 135 days.
What USDA hardiness zone is Idaho?
Idaho falls in USDA hardiness zones 3b-7a. This affects which perennial plants will survive winter and influences optimal planting times.
When is the first frost in Idaho?
The average first frost date in Idaho is Sep 25. Plan to harvest cold-sensitive crops before this date or protect them with row covers.
How long is the growing season in Idaho?
Idaho has an average growing season of 135 days, from the last frost (May 15) to first frost (Sep 25). This shorter season requires starting many crops indoors and choosing quick-maturing varieties.
Plan Your Garden
Use our seed starting calculator to get personalized planting dates, or browse all states.