Idaho Planting Zones by City and ZIP Code
Idaho runs from zones 4a to 7b; 28% of its ZIPs are 6b, Boise is 7a and Idaho Falls is 5b.
Idaho runs from zones 4a to 7b
The coldest night of the winter averages -30°F to -25°F in the coldest of Idaho’s ZIP codes and 5°F to 10°F in the warmest. Most of the state is zone 6b.
Planting zones of Idaho cities
| City | Zone | Coldest night, on average | Since 2012 |
|---|---|---|---|
| Boise83702 | 7a | 0°F to 5°F | same as 2012 |
| Idaho Falls83402 | 5b | -15°F to -10°F | half a zone warmer than 2012 (5a) |
| Coeur d'Alene83814 | 6b | -5°F to 0°F | half a zone colder than 2012 (7a) |
| Twin Falls83301 | 6b | -5°F to 0°F | same as 2012 |
| Pocatello83201 | 6b | -5°F to 0°F | half a zone warmer than 2012 (6a) |
| Lewiston83501 | 7b | 5°F to 10°F | same as 2012 |
Tap a ZIP for that address’s frost dates and this month’s jobs.
Find your zone anywhere in Idaho
A ZIP code or a town gives you its zone, how it moved since 2012, the frost dates at the nearest NOAA station, and the jobs for this month timed from them.
What to plant in Idaho this month
The calendar for each of Idaho's main zones, from vegetables to pruning and winter protection, each job tied to the extension page it comes from. Pick a month, or read the whole year below it.
Timed from the median frost dates of the 24 NOAA stations in Idaho’s zone 6b: last spring frost May 10, first fall frost Oct 2. Your own ZIP’s frost dates move every window, so the ZIP tool times them for you.
Pick a month above to see every job in it.
The year at a glance
- Start vegetable seeds indoorsFeb to May
- Sow vegetables in the gardenApr to May
- Sow the fall vegetable gardenJun to Aug
- Set out transplantsApr to May
- Plant trees and shrubsMar 29 to May 24 and Sep 18 to Nov 6
- Plant garlicSep 18 to Oct 23
- Plant tulips and other spring bulbsOct 9 to Oct 16
- Divide fall-blooming perennialsApr 19 to May 31
- Divide spring and summer-blooming perennialsAug 21 to Oct 2
- Prune trees and summer-flowering shrubs while dormantMar 1 to Apr 12
- Prune spring-flowering shrubs after they bloomApr 26 to Jun 21
- Water evergreens and new plantings until the ground freezesSep 4 to Nov 13
- Mulch perennial crowns once the ground freezesNov 13 to Nov 27
- Pull back the winter mulchMar 22 to Apr 5
- Put hardware cloth around young tree trunksOct 2 to Nov 13
- Dig and store dahlia and gladiolusOct 2 to Oct 9
- Cut back perennials after a hard freezeOct 9 to Nov 6
What changed in Idaho since 2012
Every ZIP on both mapsCompared ZIP by ZIP from the 2023 and 2012 USDA tables; 313 Idaho ZIP codes appear in both.
Why Idaho’s zones moved
Of the cities above, Idaho Falls went from 5a to 5b, Coeur d'Alene went from 7a to 6b and Pocatello went from 6a to 6b.
The USDA explains the national picture: “When compared to the 2012 map, the 2023 version reveals that about half of the country shifted to the next warmer half zone, and the other half of the country remained in the same half zone.” The new map uses 1991 to 2020 and more than 13,000 weather stations, so it draws Idaho’s hills, valleys and cities more finely than the 2012 map did.
A warmer zone changes which perennials and shrubs come through the winter, not when the garden gets planted; that still follows the frost dates.
Frost dates and seed starting in Idaho
Idaho planting zone questions
Planting zones by state
Sources. USDA Plant Hardiness Zone Map, ZIP code tables (2023 and 2012), PRISM Climate Group, Oregon State University; USDA Plant Hardiness Zone Map; USDA Unveils Updated Plant Hardiness Zone Map (USDA Agricultural Research Service, November 15, 2023); NOAA NCEI U.S. Climate Normals 1991-2020, annual/seasonal, by station (v1.0.1); NC State Extension Gardener Plant Toolbox. Zones are read from the PRISM ZIP code tables, read Oct 9, 2026; a ZIP code’s zone is the zone at its center. The calendar’s extension sources are listed on the planting zones page and under each job.