USDA hardiness zones in Idaho
| Zone | Avg. extreme minimum | ZIP codes | Example cities |
|---|---|---|---|
| Zone 4a | −30 to −25°F | 2 | — |
| Zone 4b | −25 to −20°F | 2 | — |
| Zone 5a | −20 to −15°F | 40 | Rexburg |
| Zone 5b | −15 to −10°F | 39 | Idaho Falls, Ammon, Blackfoot, Rigby |
| Zone 6a | −10 to −5°F | 53 | Pocatello, Hailey, Rupert, Preston |
| Zone 6b | −5 to 0°F | 86 | Coeur d'Alene, Post Falls, Moscow, Hayden |
| Zone 7a | 0 to 5°F | 63 | Boise, Meridian, Nampa, Caldwell |
| Zone 7b | 5 to 10°F | 2 | — |
Growing zone and frost dates by city
| City | Zone | Frost dates |
|---|---|---|
| Boise | 7a (0 to 5°F) | Boise frost dates |
| Meridian | 7a (0 to 5°F) | Meridian frost dates |
| Nampa | 7a (0 to 5°F) | Nampa frost dates |
| Caldwell | 7a (0 to 5°F) | Caldwell frost dates |
| Idaho Falls | 5b (−15 to −10°F) | Idaho Falls frost dates |
| Pocatello | 6a (−10 to −5°F) | Pocatello frost dates |
| Coeur d'Alene | 6b (−5 to 0°F) | Coeur d'Alene frost dates |
| Twin Falls | 7a (0 to 5°F) | Twin Falls frost dates |
| Post Falls | 6b (−5 to 0°F) | Post Falls frost dates |
| Rexburg | 5a (−20 to −15°F) | Rexburg frost dates |
| Lewiston | 7a (0 to 5°F) | Lewiston frost dates |
| Eagle | 7a (0 to 5°F) | Eagle frost dates |
| Kuna | 7a (0 to 5°F) | Kuna frost dates |
| Moscow | 6b (−5 to 0°F) | Moscow frost dates |
| Star | 7a (0 to 5°F) | Star frost dates |
| Ammon | 5b (−15 to −10°F) | Ammon frost dates |
| Hayden | 6b (−5 to 0°F) | Hayden frost dates |
| Chubbuck | 6b (−5 to 0°F) | Chubbuck frost dates |
| Mountain Home | 7a (0 to 5°F) | Mountain Home frost dates |
| Jerome | 6b (−5 to 0°F) | Jerome frost dates |
| Blackfoot | 5b (−15 to −10°F) | Blackfoot frost dates |
| Rathdrum | 6b (−5 to 0°F) | Rathdrum frost dates |
| Garden City | 7a (0 to 5°F) | Garden City frost dates |
| Middleton | 7a (0 to 5°F) | Middleton frost dates |
| Burley | 6b (−5 to 0°F) | Burley frost dates |
| Sandpoint | 6b (−5 to 0°F) | Sandpoint frost dates |
| Hailey | 6a (−10 to −5°F) | Hailey frost dates |
| Emmett | 7a (0 to 5°F) | Emmett frost dates |
| Payette | 7a (0 to 5°F) | Payette frost dates |
| Fruitland | 7a (0 to 5°F) | Fruitland frost dates |
| Rupert | 6a (−10 to −5°F) | Rupert frost dates |
| Weiser | 7a (0 to 5°F) | Weiser frost dates |
| Preston | 6a (−10 to −5°F) | Preston frost dates |
| Kimberly | 6b (−5 to 0°F) | Kimberly frost dates |
| Rigby | 5b (−15 to −10°F) | Rigby frost dates |
| Shelley | 5b (−15 to −10°F) | Shelley frost dates |
Frequently asked questions
What growing zone is Idaho in?
Idaho’s ZIP codes span USDA zones 4a to 7b, and 6b is the most common. Zones vary with elevation and distance from water, so check your own ZIP code.
When should I plant?
Hardiness zones are about winter cold, not planting dates. For timing, use the last spring frost date for your city on our Idaho frost dates page.