Your zone is set by how cold your winters get: the average coldest night of the year at your place, over 1991 to 2020. Each zone covers 10 °F, from zone 1 (−60 °F) to zone 13 (70 °F), and is split into an “a” half and a warmer “b” half of 5 °F each. A plant labeled hardy to your zone, or a colder one, should survive your winters.
What the zone numbers mean
The USDA divides the country into 13 zones by the average annual extreme minimum temperature: the lowest temperature of each winter, averaged over 30 years.
| Zone | Average coldest night | “a” half | “b” half |
|---|---|---|---|
| 1 | −60 to −50 °F | −60 to −55 | −55 to −50 |
| 2 | −50 to −40 °F | −50 to −45 | −45 to −40 |
| 3 | −40 to −30 °F | −40 to −35 | −35 to −30 |
| 4 | −30 to −20 °F | −30 to −25 | −25 to −20 |
| 5 | −20 to −10 °F | −20 to −15 | −15 to −10 |
| 6 | −10 to 0 °F | −10 to −5 | −5 to 0 |
| 7 | 0 to 10 °F | 0 to 5 | 5 to 10 |
| 8 | 10 to 20 °F | 10 to 15 | 15 to 20 |
| 9 | 20 to 30 °F | 20 to 25 | 25 to 30 |
| 10 | 30 to 40 °F | 30 to 35 | 35 to 40 |
| 11 | 40 to 50 °F | 40 to 45 | 45 to 50 |
| 12 | 50 to 60 °F | 50 to 55 | 55 to 60 |
| 13 | 60 to 70 °F | 60 to 65 | 65 to 70 |
Zones 1 and 2 are found only in Alaska; zones 12 and 13 in Hawaii and Puerto Rico.
Zones by state
Most states span several half zones, from mountains to coast. The “most common” zone is the one the most ZIP codes fall in, so it leans toward where people live.
| State | Zones | Most common | Share of ZIP codes |
|---|---|---|---|
| Alabama | 7b–9b | 8b | 42% |
| Alaska | 1a–8b | 5a | 12% |
| Arizona | 5b–10a | 9b | 39% |
| Arkansas | 7a–8b | 8a | 54% |
| California | 5b–11a | 9b | 34% |
| Colorado | 4a–7a | 6a | 44% |
| Connecticut | 6a–7b | 6b | 60% |
| Delaware | 7a–8a | 7b | 95% |
| District of Columbia | 7b–8a | 8a | 85% |
| Florida | 8b–11b | 10a | 30% |
| Georgia | 7a–9a | 8a | 41% |
| Hawaii | 10b–13a | 12b | 71% |
| Idaho | 4a–7b | 6b | 28% |
| Illinois | 5a–7a | 6a | 42% |
| Indiana | 5b–7a | 6a | 61% |
| Iowa | 4b–6a | 5a | 54% |
| Kansas | 6a–7a | 6b | 54% |
| Kentucky | 6b–7b | 7a | 78% |
| Louisiana | 8b–10a | 9a | 48% |
| Maine | 3b–7a | 5a | 32% |
| Maryland | 6a–8a | 7b | 61% |
| Massachusetts | 5b–7b | 6b | 42% |
| Michigan | 4a–7a | 6a | 55% |
| Minnesota | 3a–5a | 4b | 36% |
| Mississippi | 7b–9a | 8b | 58% |
| Missouri | 5b–8a | 6b | 46% |
| Montana | 3b–6b | 4b | 32% |
| Nebraska | 5a–6a | 5b | 48% |
| Nevada | 5a–10a | 9b | 24% |
| New Hampshire | 4a–6b | 6a | 42% |
| New Jersey | 6b–8a | 7a | 47% |
| New Mexico | 5a–8b | 7b | 25% |
| New York | 4a–7b | 6a | 24% |
| North Carolina | 6b–9a | 8a | 60% |
| North Dakota | 3b–4b | 4a | 78% |
| Ohio | 6a–7a | 6b | 56% |
| Oklahoma | 6b–8a | 7b | 60% |
| Oregon | 5b–9b | 8b | 40% |
| Pennsylvania | 5b–8a | 6b | 36% |
| Puerto Rico | 11b–13b | 13a | 57% |
| Rhode Island | 6b–7b | 7a | 53% |
| South Carolina | 8a–9b | 8b | 50% |
| South Dakota | 4a–5b | 4b | 48% |
| Tennessee | 6b–8a | 7b | 70% |
| Texas | 6b–10b | 8b | 38% |
| Utah | 4a–8b | 6a | 32% |
| Vermont | 4a–6a | 5a | 58% |
| Virginia | 6a–8b | 7b | 43% |
| Washington | 6a–9b | 8b | 37% |
| West Virginia | 5b–7a | 7a | 49% |
| Wisconsin | 3b–6a | 5b | 30% |
| Wyoming | 4a–5b | 5a | 58% |
Our count from the PRISM Group’s 2023 ZIP-code listing, with ZIP codes assigned to states by their first three digits.
How to use your zone
- Perennials, shrubs and trees: plant labels and catalogs give the coldest zone a plant survives, such as “hardy to zone 5”. If your zone is that number or warmer, it should come through a normal winter.
- Planting dates: our guides list planting windows by zone, such as when to plant garlic or tulip bulbs.
- Frost dates: for annuals and vegetables, the dates of your last spring and first fall frost matter more than the zone. The finder shows them; see frost dates by ZIP code for the odds.
What your zone doesn’t tell you
- It’s an average, not a record. The USDA says the zones don’t reflect the coldest it has ever been or ever will be at a place, and that the coldest night varies a lot from year to year.
- Your yard can differ. The 2023 map is built on an 800-meter grid (400 meters in Hawaii and Puerto Rico, PRISM Group), and a ZIP code covers a larger area than that. Cold air settles into low spots on still nights (Penn State Extension), and a sheltered wall or a city stays warmer.
- Winter cold isn’t the only limit. Summer heat, rainfall and soil decide what thrives too; the zone only says what should survive the cold.
Did my zone change in 2023?
Possibly. The USDA released the current map on November 15, 2023, using weather data from 1991 to 2020 at 13,412 stations, against 7,983 for the 2012 map. About half the country moved to the next warmer half zone; the other half stayed in the same half zone. The USDA notes that the changes mostly come from using a newer 30-year period, and are not necessarily a measure of climate change.
Questions people ask
What is the difference between zone 7a and 7b?
5 °F of winter cold. Zone 7 covers average coldest nights of 0 to 10 °F; 7a is the colder half (0 to 5 °F) and 7b the warmer (5 to 10 °F).
Is my growing zone the same as my planting zone?
Yes. Growing zone, planting zone, gardening zone and hardiness zone all mean the USDA plant hardiness zone.
What zone is my state?
Most states span several zones; see the zones by state table, or enter your ZIP code for your own.
Why does my ZIP code show a different zone than my town’s neighbor?
Zones change with elevation, nearby water and city heat. A ZIP code gets one zone, which may not match every yard in it, especially in hills; the USDA’s interactive map shows the zone for an exact address.
Where do the frost dates come from?
From NOAA’s 1991–2020 climate normals for a weather station near your ZIP code. The finder names the station and how far away it is.
Sources
- USDA Agricultural Research Service, USDA Unveils Updated Plant Hardiness Zone Map (November 15, 2023): 13 zones of 10 °F in 5 °F halves; the average annual extreme minimum temperature, 1991–2020; 13,412 stations against 7,983; about half the country a half zone warmer; not the coldest ever; not necessarily climate change.
- USDA Plant Hardiness Zone Map (2023), with the interactive map by address.
- Zones by ZIP code: PRISM Group, Oregon State University, 2023 USDA Plant Hardiness Zone GIS Datasets, 800 m grids (400 m in Hawaii and Puerto Rico) and ZIP-code listings for the US, Alaska, Hawaii and Puerto Rico, prism.oregonstate.edu, accessed October 11, 2026.
- Frost dates: NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual freeze-date probabilities by station; ZIP code centers from the U.S. Census Bureau’s 2024 Gazetteer files.
- Penn State Extension, Frost, Critical Temperatures, and Frost Protection (Rob Crassweller, 2024): cold air flows down into low areas.