What Hardiness Zone Is Idaho?

Q: What hardiness zone is Idaho?

Idaho is in USDA hardiness zones 4a–7b on the 2023 USDA Plant Hardiness Zone Map. Zone 6b is the most common, covering 28% of Idaho's ZIP codes, and zone 7a covers 26%. Enter your ZIP code for your exact zone.

Q: What does zone 6b mean?

Zone 6b means the average annual extreme minimum temperature, the coldest night of a typical winter, is −5°F to 0°F (−21°C to −18°C). Perennials, shrubs and trees rated for zone 6b or colder should survive winter there.

Q: What is the coldest hardiness zone in Idaho?

Zone 4a is the coldest zone mapped in Idaho, found around Island Park, and zone 7b is the warmest.

Q: Did Idaho's hardiness zones change in 2023?

The USDA released a new Plant Hardiness Zone Map in November 2023, based on 1991–2020 temperatures instead of 1976–2005. About half of the United States shifted half a zone warmer. Check your ZIP code here, because plant tags and older books may still list your 2012 zone.

Q: When should I plant in zone 6b?

Hardiness zones don't set planting dates; frost dates do. Inside zone 6b in Idaho, the median last spring frost varies from April 22 to June 17. Look up your local frost dates and plant tender crops such as tomatoes after the 10%-risk last-frost date.

USDA 2023 Plant Hardiness Zone Map · 313 ZIP codes · Data updated 2026-10-28

Quick answer

Idaho spans USDA hardiness zones 4a–7b on the 2023 Plant Hardiness Zone Map. The most common zone is 6b, covering 28% of Idaho's ZIP codes, followed by zone 7a (26%). Zone 6b means the coldest night of an average winter reaches −5°F to 0°F (−21°C to −18°C). Enter your ZIP code for your exact zone.

Idaho hardiness zones by share of ZIP codes

Zone 4a<1% · 2 ZIPs

Zone 4b<1% · 2 ZIPs

Zone 5a13% · 41 ZIPs

Zone 5b14% · 44 ZIPs

Zone 6a17% · 52 ZIPs

Zone 6b28% · 87 ZIPs

Zone 7a26% · 82 ZIPs

Zone 7b<1% · 3 ZIPs

What the zones mean for Idaho gardeners

Coldest and warmest towns: among towns with NOAA weather stations, Island Park (6,290 ft) is in zone 4a, while Dworshak Fish Hatchery (995 ft) is in zone 7a. That is a difference of about 30°F in the coldest night of a typical winter.
Same zone, different frost dates: within zone 6b, the median last spring frost ranges from April 22 at Coeur D'alene to June 17 at Idaho City, 56 days apart. Your zone tells you which perennials survive winter; your frost dates tell you when to plant.

Typical frost dates in each Idaho zone

Medians across NOAA weather stations in each zone. Colder zones usually have later spring frosts, but local terrain can shift the dates by weeks.

Zone	Last spring frost	First fall frost	Stations
5a	June 3	September 11	11
5b	May 23	September 20	10
6a	May 16	September 29	16
6b	May 13	October 2	24
7a	April 29	October 11	17

Hardiness zones for Idaho cities

Zones at the National Weather Service stations, mostly city airports, with their median frost dates.


Boise Air Terminal	7a	0°F to 5°F	2,814	Apr 24	Oct 21
Burley Municipal Airport	6b	−5°F to 0°F	4,142	May 7	Oct 4
Idaho Falls Fanning Field	5b	−15°F to −10°F	4,729	May 23	Sep 20
Jerome County Airport	6b	−5°F to 0°F	4,048	May 1	Oct 14
Malad City	6a	−10°F to −5°F	4,470	May 22	Sep 20
Mullan Pass Vor/dme	6a	−10°F to −5°F	6,028	Jun 10	Sep 23
Twin Falls Sun Valley Regional Airport	6b	−5°F to 0°F	4,151	May 9	Oct 4

Hardiness zones for 85 towns in Idaho

Each NOAA weather station is shown with the USDA zone of the nearest ZIP code (within 8 miles). Coldest night is the zone's range for the average annual extreme minimum temperature. Click a column to sort.

Filter by town


Aberdeen Experiment Station	5b	−15°F to −10°F	4,405	May 21	Sep 20
Ashton 1N	5a	−20°F to −15°F	5,212	May 21	Sep 21
Bayview Model Basin	6b	−5°F to 0°F	2,087	May 22	Sep 22
Bellevue	6a	−10°F to −5°F	5,192	May 13	Oct 2
Bern	5a	−20°F to −15°F	5,964	Jun 17	Sep 3
Boise 7 N	7a	0°F to 5°F	3,885	May 17	Oct 12
Boise Air Terminal	7a	0°F to 5°F	2,814	Apr 24	Oct 21
Boise Lucky Peak Dam	7a	0°F to 5°F	2,840	Apr 30	Oct 22
Brownlee Dam	7a	0°F to 5°F	1,844	Apr 2	Nov 5
Buhl #2	7a	0°F to 5°F	3,800	Apr 25	Oct 15
Burley Municipal Airport	6b	−5°F to 0°F	4,142	May 7	Oct 4
Cabinet Gorge	6b	−5°F to 0°F	2,173	May 9	Oct 8
Castleford 2 N	7a	0°F to 5°F	3,825	May 17	Sep 29
Chilly Barton Flat	5a	−20°F to −15°F	6,260	Jun 14	Sep 8
Coeur D'alene	6b	−5°F to 0°F	2,133	Apr 22	Oct 18
Cottonwood 2 WSW	6a	−10°F to −5°F	3,945	May 6	Oct 13
Council	6a	−10°F to −5°F	2,943	May 10	Oct 2
Downey	6b	−5°F to 0°F	4,865	May 31	Sep 18
Dworshak Fish Hatchery	7a	0°F to 5°F	995	Apr 20	Oct 20
Elk River	6b	−5°F to 0°F	2,866	May 16	Sep 23
Emmett 2 E	7a	0°F to 5°F	2,390	Apr 30	Oct 17
Fort Hall 1 NNE	5b	−15°F to −10°F	4,465	May 20	Sep 20
Garden Valley	6b	−5°F to 0°F	3,100	Jun 1	Sep 10
Gibbonsville #2	5b	−15°F to −10°F	4,480	Jun 1	Sep 17
Glenns Ferry	7a	0°F to 5°F	2,466	May 1	Oct 3
Grace	5b	−15°F to −10°F	5,550	May 29	Sep 17
Grand View 4 NW	7a	0°F to 5°F	2,400	Apr 28	Oct 6
Grangeville	6b	−5°F to 0°F	3,300	May 9	Oct 3
Hagerman 2 SW	7a	0°F to 5°F	2,897	May 3	Oct 1
Hamer 4 NW	5a	−20°F to −15°F	4,790	Jun 3	Sep 11
Hazelton	6b	−5°F to 0°F	4,060	May 7	Oct 5
Headquarters	6a	−10°F to −5°F	3,200	Any month	Any month
Hill City 1 W	5a	−20°F to −15°F	5,100	Jun 16	Sep 6
Homedale 1 SE	7a	0°F to 5°F	2,230	Apr 24	Oct 9
Idaho City	6b	−5°F to 0°F	3,965	Jun 17	Sep 5
Idaho Falls - Kifi	5b	−15°F to −10°F	4,742	May 9	Oct 1
Idaho Falls 16 SE	5b	−15°F to −10°F	5,828	Jun 9	Sep 11
Idaho Falls Fanning Field	5b	−15°F to −10°F	4,729	May 23	Sep 20
Island Park	4a	−30°F to −25°F	6,290	Any month	Any month
Jerome County Airport	6b	−5°F to 0°F	4,048	May 1	Oct 14
Kamiah	7a	0°F to 5°F	1,210	Apr 29	Oct 5
Kellogg	6b	−5°F to 0°F	2,377	May 14	Sep 26
Ketchum Ranger Station	5b	−15°F to −10°F	5,890	Any month	Any month
Kooskia 5 SSE	7a	0°F to 5°F	2,330	Apr 30	Oct 11
Lava Hot Springs	6b	−5°F to 0°F	4,595	May 21	Sep 21
Lifton Pumping Station	5a	−20°F to −15°F	5,935	May 19	Sep 21
Malad City	6a	−10°F to −5°F	4,470	May 22	Sep 20
Massacre Rocks State Park	6a	−10°F to −5°F	4,195	May 20	Sep 26
May 2SSE	5a	−20°F to −15°F	5,050	Jun 12	Sep 6
McCammon	5b	−15°F to −10°F	4,770	May 23	Sep 24
Minidoka Dam	6a	−10°F to −5°F	4,164	May 16	Oct 1
Monteview	4b	−25°F to −20°F	4,815	Jun 12	Sep 7
Moscow U Of I	6b	−5°F to 0°F	2,660	Any month	Any month
Mullan	6a	−10°F to −5°F	3,201	May 12	Sep 30
Mullan Pass Vor/dme	6a	−10°F to −5°F	6,028	Jun 10	Sep 23
Nampa Sugar Factory	7a	0°F to 5°F	2,470	Apr 29	Oct 13
Nezperce	6b	−5°F to 0°F	3,248	May 24	Sep 20
Oakley	6b	−5°F to 0°F	4,559	May 15	Oct 2
Ola	7a	0°F to 5°F	3,075	May 31	Sep 16
Parma Experiment Station	7a	0°F to 5°F	2,290	Apr 27	Oct 9
Paul 1ENE	6a	−10°F to −5°F	4,150	May 6	Oct 6
Picabo	6a	−10°F to −5°F	4,839	Jun 16	Sep 9
Plummer 3 WSW	6b	−5°F to 0°F	2,905	May 11	Oct 5
Pocatello 2 NE	6b	−5°F to 0°F	4,832	May 16	Oct 2
Pocatello City	6a	−10°F to −5°F	4,460	May 2	Oct 11
Potlatch 3 NNE	6b	−5°F to 0°F	2,760	May 15	Sep 21
Preston	6a	−10°F to −5°F	4,719	May 16	Sep 28
Prichard 3 ESE	6a	−10°F to −5°F	2,547	May 31	Sep 5
Priest River Experiment Station	6a	−10°F to −5°F	2,371	May 20	Sep 13
Red River Ranger Station	5b	−15°F to −10°F	4,350	Any month	Any month
Rexburg Byu Idaho	5a	−20°F to −15°F	5,005	May 12	Sep 24
Richfield	6a	−10°F to −5°F	4,309	May 24	Sep 26
Rigby	5b	−15°F to −10°F	4,856	May 9	Oct 5
Riggins	6b	−5°F to 0°F	2,056	May 6	Oct 9
Saint Anthony	5a	−20°F to −15°F	4,910	May 17	Sep 22
Saint Maries	6b	−5°F to 0°F	2,151	May 3	Oct 4
Sandpoint Experiment Station	6b	−5°F to 0°F	2,126	May 8	Sep 28
Shoshone 1 WNW	6a	−10°F to −5°F	3,950	Apr 24	Oct 16
Small 6N	5b	−15°F to −10°F	5,740	Jun 5	Sep 20
Sugar City	5a	−20°F to −15°F	4,925	May 29	Sep 13
Swan Valley	6a	−10°F to −5°F	5,397	Any month	Any month
Tetonia Experiment Station	5a	−20°F to −15°F	6,170	Jun 15	Sep 7
Twin Falls Sun Valley Regional Airport	6b	−5°F to 0°F	4,151	May 9	Oct 4
Wallace	6b	−5°F to 0°F	2,710	May 5	Oct 2
Winchester	6b	−5°F to 0°F	3,972	May 23	Sep 25

Frequently asked questions

What hardiness zone is Idaho?

Idaho is in USDA hardiness zones 4a–7b on the 2023 USDA Plant Hardiness Zone Map. Zone 6b is the most common, covering 28% of Idaho's ZIP codes, and zone 7a covers 26%. Enter your ZIP code for your exact zone.

What does zone 6b mean?

Zone 6b means the average annual extreme minimum temperature, the coldest night of a typical winter, is −5°F to 0°F (−21°C to −18°C). Perennials, shrubs and trees rated for zone 6b or colder should survive winter there.

What is the coldest hardiness zone in Idaho?

Zone 4a is the coldest zone mapped in Idaho, found around Island Park, and zone 7b is the warmest.

Did Idaho's hardiness zones change in 2023?

The USDA released a new Plant Hardiness Zone Map in November 2023, based on 1991–2020 temperatures instead of 1976–2005. About half of the United States shifted half a zone warmer. Check your ZIP code here, because plant tags and older books may still list your 2012 zone.

When should I plant in zone 6b?

Hardiness zones don't set planting dates; frost dates do. Inside zone 6b in Idaho, the median last spring frost varies from April 22 to June 17. Look up your local frost dates and plant tender crops such as tomatoes after the 10%-risk last-frost date.

Zone and frost dates: use both

Your hardiness zone answers one question: will this plant survive the winter here? Choose perennials, shrubs, trees and bulbs rated for your zone or a colder one. For vegetables and annuals, what matters is the length of the frost-free season. See Idaho frost dates by town, or get a planting calendar for your ZIP code with start-indoors, transplant and sowing dates for 30 crops.

Sources and method

Zones are from the USDA 2023 Plant Hardiness Zone Map ZIP-code files published by the PRISM Climate Group, Oregon State University, based on 1991–2020 minimum temperatures. ZIP codes are assigned to states by USPS prefix. Town zones use the ZIP code nearest each NOAA 1991–2020 Climate Normals station. This is an independent tool, not an official USDA site. Full methodology.