Who Moved Hardiness Zones: 2012 vs 2023 USDA Maps by State
We set every ZIP code's half zone on the 2023 USDA Plant Hardiness Zone Map beside its half zone on the 2012 map, and counted the people who live there. 55.8% of Americans, about 186.7 million people, live in a ZIP code whose half zone moved warmer; 43.1% saw no change and 1.1% moved colder.
Key findings
- 55.8%Americans in a ZIP code that moved to a warmer half zone (186.7 million people)
- 0.7%Moved a full zone or more warmer
- 43.1%Kept the same half zone
- 1.1%Moved to a colder half zone
- 33 of 51States (counting DC) where most people moved warmer
- 100.0%Highest share moved warmer: District of Columbia; lowest: Hawaii, 6.9%
What a half zone means
Each USDA zone is a 10 °F band of the average annual extreme minimum temperature: the coldest night of each winter, averaged over thirty winters. In the USDA's words, the map is "displayed as 10-degree F zones and 5-degree F half zones." So zone 6 covers −10 to 0 °F; its colder half, 6a, covers −10 to −5 °F and its warmer half, 6b, −5 to 0 °F. A move of one half zone, say from 6a to 6b, means the thirty-year average of the coldest night now falls in the next 5 °F band up.
That does not mean the place got 5 °F warmer. PRISM's ZIP code lists give only the band, not the temperature inside it, so a ZIP code sitting just under a band's edge can cross it with a small change, while one at the bottom of a band can warm by several degrees and keep its label. The USDA's own estimate of the average shift, a quarter of a zone, is about 2.5 °F, and that is how a small average shift can move about half the country into a new half zone: a small, broad shift pushes the places near the top of their band over it and leaves the rest where they were. That fits what the ZIP codes show: 55.1% of people are in a ZIP code that moved exactly one half zone warmer, and only 0.7% in one that moved further.
State by state
The states with the largest share of people in a ZIP code that moved warmer are District of Columbia (100.0%), Tennessee (89.3%), Missouri (85.4%), Delaware (84.7%) and Alabama (83.6%). In the District of Columbia, 100.0% of ZIP codes moved warmer, and 34.7% of its people are in ZIP codes that moved a full zone. The smallest shares are in Hawaii (6.9%), North Dakota (12.6%), Arizona (21.7%), California (22.9%) and Iowa (28.1%); in Puerto Rico, which the tile map leaves out, the figure is 13.4%.
Moves to a colder half zone are rare. In 24 of the 51 states, not one ZIP code moved colder. The largest colder shares of people are in Utah (12.9%), Alaska (10.2%), Hawaii (8.9%) and Wyoming (7.2%). Alaska moved both ways at once: 15.6% of its people are in ZIP codes that moved a full zone or more warmer, more than any state but the District of Columbia, while 10.2% are in ZIP codes that moved colder. The USDA notes that "The most substantial changes produced by additional data sources and improved interpolation methods are seen in upland areas of Alaska."
Across the 50 states and DC, 562 of 40,304 ZIP codes moved a full zone or more warmer and 436 moved colder. The biggest single moves are 5 half zones warmer (California and Alaska) and 6 half zones colder (California and Alaska), far beyond the quarter-zone average shift the USDA describes.
| State | People | Warmer by a half zone | Warmer by a full zone or more | No change | Colder | All warmer |
|---|---|---|---|---|---|---|
| United States (50 states and DC) | 334,468,895 | 55.1% | 0.7% | 43.1% | 1.1% | 55.8% |
| District of Columbia | 678,125 | 65.3% | 34.7% | 0.0% | 0.0% | 100.0% |
| Tennessee | 7,057,459 | 88.6% | 0.7% | 10.7% | 0.0% | 89.3% |
| Missouri | 6,191,536 | 77.9% | 7.5% | 14.6% | 0.0% | 85.4% |
| Delaware | 1,021,024 | 84.7% | 0.0% | 15.3% | 0.0% | 84.7% |
| Alabama | 5,084,799 | 83.4% | 0.2% | 16.4% | 0.0% | 83.6% |
| Kansas | 2,946,425 | 81.9% | 0.0% | 18.1% | 0.0% | 81.9% |
| Oklahoma | 4,028,317 | 79.0% | 0.0% | 21.0% | 0.0% | 79.0% |
| Kentucky | 4,539,249 | 77.9% | 0.8% | 21.3% | 0.0% | 78.7% |
| West Virginia | 1,777,802 | 77.9% | 0.6% | 21.5% | 0.0% | 78.5% |
| Texas | 30,093,371 | 76.7% | 0.0% | 23.1% | 0.2% | 76.7% |
| Maryland | 6,204,738 | 75.4% | 1.0% | 23.4% | 0.2% | 76.4% |
| Georgia | 10,935,509 | 72.9% | 0.4% | 26.7% | 0.0% | 73.3% |
| North Carolina | 10,728,861 | 73.1% | 0.2% | 26.7% | 0.0% | 73.3% |
| Arkansas | 2,999,210 | 71.9% | 0.6% | 27.5% | 0.0% | 72.5% |
| Alaska | 735,134 | 56.7% | 15.6% | 17.5% | 10.2% | 72.3% |
| Nebraska | 1,979,371 | 68.0% | 0.0% | 32.0% | 0.0% | 68.0% |
| Virginia | 8,698,099 | 66.4% | 1.3% | 32.1% | 0.2% | 67.7% |
| New Hampshire | 1,394,951 | 66.2% | 0.9% | 32.5% | 0.4% | 67.1% |
| Pennsylvania | 13,002,189 | 65.8% | 0.5% | 33.3% | 0.4% | 66.3% |
| Rhode Island | 1,101,173 | 65.9% | 0.0% | 34.1% | 0.0% | 65.9% |
| Mississippi | 2,944,861 | 65.3% | 0.0% | 34.7% | 0.0% | 65.3% |
| Ohio | 11,805,998 | 64.0% | 0.6% | 35.4% | 0.0% | 64.6% |
| Minnesota | 5,737,732 | 62.5% | 0.0% | 37.3% | 0.3% | 62.5% |
| Montana | 1,116,943 | 55.4% | 7.0% | 36.5% | 1.2% | 62.4% |
| New Jersey | 9,338,367 | 62.0% | 0.0% | 38.0% | 0.0% | 62.0% |
| Vermont | 647,042 | 59.5% | 2.1% | 38.4% | 0.0% | 61.6% |
| Florida | 22,415,340 | 61.3% | 0.2% | 38.5% | 0.0% | 61.5% |
| Indiana | 6,848,599 | 59.7% | 0.1% | 40.2% | 0.0% | 59.8% |
| Nevada | 3,184,080 | 56.3% | 3.0% | 36.9% | 3.7% | 59.3% |
| South Carolina | 5,291,741 | 55.9% | 1.4% | 42.7% | 0.0% | 57.3% |
| South Dakota | 905,091 | 51.3% | 0.0% | 45.1% | 3.5% | 51.3% |
| Wisconsin | 5,914,155 | 51.0% | 0.0% | 48.9% | 0.1% | 51.0% |
| Massachusetts | 7,040,010 | 50.3% | 0.5% | 49.1% | 0.0% | 50.9% |
| Colorado | 5,861,100 | 47.0% | 1.7% | 49.2% | 2.1% | 48.7% |
| Maine | 1,387,653 | 46.9% | 1.2% | 50.2% | 1.6% | 48.2% |
| Illinois | 12,673,213 | 46.1% | 0.8% | 53.1% | 0.0% | 46.9% |
| Louisiana | 4,606,227 | 44.0% | 0.1% | 56.0% | 0.0% | 44.0% |
| New York | 19,676,379 | 43.4% | 0.3% | 56.2% | 0.0% | 43.7% |
| Connecticut | 3,624,027 | 43.5% | 0.0% | 56.5% | 0.0% | 43.5% |
| Wyoming | 581,787 | 40.4% | 3.0% | 49.4% | 7.2% | 43.4% |
| Washington | 7,811,713 | 43.3% | 0.1% | 55.0% | 1.6% | 43.4% |
| Utah | 3,388,149 | 39.3% | 0.1% | 47.6% | 12.9% | 39.4% |
| Michigan | 10,077,333 | 38.6% | 0.6% | 60.5% | 0.3% | 39.2% |
| Idaho | 1,933,984 | 32.9% | 1.3% | 63.1% | 2.6% | 34.2% |
| New Mexico | 2,118,558 | 29.5% | 2.7% | 64.2% | 3.6% | 32.2% |
| Oregon | 4,253,848 | 29.0% | 0.7% | 68.7% | 1.6% | 29.6% |
| Iowa | 3,210,490 | 27.9% | 0.3% | 71.8% | 0.1% | 28.1% |
| California | 39,274,802 | 22.9% | 0.0% | 71.8% | 5.3% | 22.9% |
| Arizona | 7,376,661 | 21.4% | 0.4% | 76.2% | 2.1% | 21.7% |
| Puerto Rico | 3,234,309 | 11.0% | 2.4% | 81.8% | 4.8% | 13.4% |
| North Dakota | 780,758 | 12.6% | 0.0% | 87.2% | 0.2% | 12.6% |
| Hawaii | 1,444,912 | 6.9% | 0.0% | 84.2% | 8.9% | 6.9% |
Counted by ZIP code instead of by people, 57.3% of ZIP codes moved warmer. The two measures differ because rural ZIP codes are many and small: a state's ZIP code share tells you about its land, the population share about where its people live. Download the state table (CSV).
| State | ZIP codes compared | Warmer by a half zone | Warmer by a full zone or more | No change | Colder | All warmer |
|---|---|---|---|---|---|---|
| United States (50 states and DC) | 40,304 | 55.9% | 1.4% | 41.7% | 1.1% | 57.3% |
| District of Columbia | 283 | 56.2% | 43.8% | 0.0% | 0.0% | 100.0% |
| Delaware | 93 | 87.1% | 0.0% | 12.9% | 0.0% | 87.1% |
| Tennessee | 774 | 84.1% | 1.6% | 14.3% | 0.0% | 85.7% |
| Alabama | 804 | 79.5% | 0.4% | 20.1% | 0.0% | 79.9% |
| Missouri | 1,144 | 76.5% | 3.0% | 20.5% | 0.0% | 79.5% |
| West Virginia | 843 | 77.6% | 1.3% | 21.0% | 0.1% | 78.9% |
| Kentucky | 933 | 77.6% | 1.2% | 21.2% | 0.0% | 78.8% |
| Maryland | 598 | 74.6% | 1.0% | 24.2% | 0.2% | 75.6% |
| Georgia | 937 | 74.3% | 0.1% | 25.6% | 0.0% | 74.4% |
| Kansas | 741 | 73.3% | 0.0% | 26.7% | 0.0% | 73.3% |
| Arkansas | 691 | 70.9% | 1.3% | 27.8% | 0.0% | 72.2% |
| North Carolina | 1,072 | 68.4% | 0.9% | 30.7% | 0.0% | 69.3% |
| Oklahoma | 761 | 67.8% | 0.1% | 32.1% | 0.0% | 67.9% |
| Mississippi | 524 | 67.6% | 0.0% | 32.4% | 0.0% | 67.6% |
| New Jersey | 715 | 67.3% | 0.3% | 32.4% | 0.0% | 67.6% |
| Texas | 2,567 | 66.8% | 0.3% | 32.8% | 0.1% | 67.1% |
| Indiana | 928 | 66.7% | 0.3% | 33.0% | 0.0% | 67.0% |
| Pennsylvania | 2,108 | 64.1% | 1.2% | 34.6% | 0.1% | 65.3% |
| Virginia | 1,196 | 63.7% | 1.4% | 34.6% | 0.3% | 65.1% |
| South Carolina | 526 | 61.2% | 1.0% | 37.8% | 0.0% | 62.2% |
| Florida | 1,454 | 61.3% | 0.3% | 38.4% | 0.0% | 61.6% |
| Vermont | 305 | 56.7% | 4.3% | 39.0% | 0.0% | 61.0% |
| Rhode Island | 88 | 60.2% | 0.0% | 39.8% | 0.0% | 60.2% |
| Maine | 478 | 54.6% | 3.6% | 40.6% | 1.3% | 58.2% |
| New Hampshire | 280 | 56.4% | 1.1% | 41.1% | 1.4% | 57.5% |
| Montana | 399 | 52.6% | 4.8% | 41.6% | 1.0% | 57.4% |
| New York | 2,123 | 55.2% | 1.0% | 43.5% | 0.3% | 56.2% |
| Massachusetts | 675 | 55.4% | 0.6% | 44.0% | 0.0% | 56.0% |
| Nebraska | 609 | 55.8% | 0.0% | 44.2% | 0.0% | 55.8% |
| Illinois | 1,544 | 54.3% | 0.4% | 45.3% | 0.0% | 54.7% |
| Ohio | 1,391 | 53.0% | 0.7% | 46.3% | 0.0% | 53.7% |
| Wyoming | 191 | 45.5% | 7.9% | 42.4% | 4.2% | 53.4% |
| Alaska | 272 | 36.8% | 16.2% | 37.5% | 9.6% | 52.9% |
| Idaho | 313 | 45.7% | 5.1% | 47.0% | 2.2% | 50.8% |
| Washington | 708 | 48.4% | 1.0% | 48.3% | 2.3% | 49.4% |
| Minnesota | 942 | 48.8% | 0.0% | 50.5% | 0.6% | 48.8% |
| Nevada | 249 | 43.8% | 3.6% | 44.6% | 8.0% | 47.4% |
| Louisiana | 710 | 47.0% | 0.1% | 52.8% | 0.0% | 47.2% |
| Colorado | 625 | 43.0% | 4.0% | 50.1% | 2.9% | 47.0% |
| Connecticut | 419 | 46.3% | 0.0% | 53.7% | 0.0% | 46.3% |
| Wisconsin | 872 | 43.3% | 0.3% | 56.1% | 0.2% | 43.7% |
| South Dakota | 382 | 42.1% | 0.3% | 57.1% | 0.5% | 42.4% |
| New Mexico | 419 | 37.0% | 4.1% | 54.4% | 4.5% | 41.1% |
| Michigan | 1,154 | 39.5% | 0.6% | 58.7% | 1.2% | 40.1% |
| Utah | 337 | 32.6% | 2.4% | 55.5% | 9.5% | 35.0% |
| Oregon | 473 | 29.0% | 1.7% | 66.2% | 3.2% | 30.7% |
| Arizona | 521 | 24.4% | 1.2% | 68.9% | 5.6% | 25.5% |
| Iowa | 1,042 | 24.2% | 0.1% | 75.4% | 0.3% | 24.3% |
| California | 2,553 | 22.7% | 0.6% | 69.8% | 6.9% | 23.3% |
| North Dakota | 405 | 20.2% | 0.0% | 79.5% | 0.2% | 20.2% |
| Puerto Rico | 176 | 17.0% | 2.3% | 76.1% | 4.5% | 19.3% |
| Hawaii | 133 | 12.8% | 0.0% | 76.7% | 10.5% | 12.8% |
The most populous ZIP codes
Of the 20 most populous ZIP codes in the comparison, 8 moved one half zone warmer, 12 kept their half zone, 0 moved a full zone or more and 0 moved colder. Each holds more than 99,000 people, as many as a small city.
| ZIP code | Near (Census place) | State | 2012 zone | 2023 zone | Change | People |
|---|---|---|---|---|---|---|
| 77494 | – | TX | 9a | 9a | No change | 140,157 |
| 08701 | Lakewood | NJ | 7a | 7a | No change | 139,149 |
| 77449 | – | TX | 9a | 9b | 1 half zone warmer | 130,028 |
| 78660 | Pflugerville | TX | 8b | 9a | 1 half zone warmer | 124,834 |
| 77433 | – | TX | 9a | 9a | No change | 116,550 |
| 77084 | – | TX | 9a | 9b | 1 half zone warmer | 110,217 |
| 60629 | Chicago | IL | 6a | 6a | No change | 108,324 |
| 11368 | New York | NY | 7b | 7b | No change | 105,716 |
| 92336 | Fontana | CA | 10a | 10a | No change | 105,517 |
| 11208 | New York | NY | 7b | 7b | No change | 105,428 |
| 37013 | Nashville-Davidson | TN | 7a | 7b | 1 half zone warmer | 105,212 |
| 78130 | New Braunfels | TX | 8b | 9a | 1 half zone warmer | 104,009 |
| 79936 | – | TX | 8a | 8b | 1 half zone warmer | 102,991 |
| 11385 | New York | NY | 7b | 7b | No change | 101,704 |
| 30044 | – | GA | 7b | 8a | 1 half zone warmer | 101,475 |
| 34787 | Horizon West | FL | 9b | 9b | No change | 101,441 |
| 94565 | Pittsburg | CA | 9b | 9b | No change | 100,488 |
| 90011 | Los Angeles | CA | 10b | 10b | No change | 100,113 |
| 90650 | Norwalk | CA | 10b | 10b | No change | 99,900 |
| 78641 | Leander | TX | 8b | 9a | 1 half zone warmer | 99,865 |
Large ZIP codes that moved a full zone or more
A full zone is two half zones, or 10 °F of band. By state, the 12 most populous ZIP codes that moved that far are in Missouri (4), District of Columbia (3), Nevada (1), Georgia (1), Puerto Rico (1), Virginia (1) and Maryland (1).
| ZIP code | Near (Census place) | State | 2012 zone | 2023 zone | Change | People |
|---|---|---|---|---|---|---|
| 89031 | Las Vegas | NV | 8b | 9b | 2 half zones warmer | 77,305 |
| 20002 | Washington | DC | 7a | 8a | 2 half zones warmer | 72,397 |
| 20019 | Washington | DC | 7a | 8a | 2 half zones warmer | 63,380 |
| 63021 | – | MO | 6a | 7a | 2 half zones warmer | 55,666 |
| 30680 | Winder | GA | 7b | 8b | 2 half zones warmer | 48,388 |
| 00959 | Bayamón | PR | 12a | 13a | 2 half zones warmer | 46,260 |
| 63303 | – | MO | 6a | 7a | 2 half zones warmer | 46,089 |
| 63026 | – | MO | 6a | 7a | 2 half zones warmer | 45,354 |
| 20001 | Washington | DC | 7a | 8a | 2 half zones warmer | 44,616 |
| 20164 | Sterling | VA | 6b | 7b | 2 half zones warmer | 43,436 |
| 21042 | – | MD | 6b | 7b | 2 half zones warmer | 43,327 |
| 63017 | Chesterfield | MO | 6a | 7a | 2 half zones warmer | 43,243 |
Large ZIP codes that moved colder
By state, the 12 most populous ZIP codes that moved to a colder half zone are in California (8), Utah (1), Puerto Rico (1), Arizona (1) and Colorado (1): a reminder that the new map redrew lines in both directions.
| ZIP code | Near (Census place) | State | 2012 zone | 2023 zone | Change | People |
|---|---|---|---|---|---|---|
| 92683 | Westminster | CA | 10b | 10a | 1 half zone colder | 89,833 |
| 92804 | – | CA | 10b | 10a | 1 half zone colder | 83,537 |
| 94544 | Hayward | CA | 10a | 9b | 1 half zone colder | 76,947 |
| 93306 | – | CA | 10a | 9b | 1 half zone colder | 74,116 |
| 94536 | – | CA | 10a | 9b | 1 half zone colder | 70,619 |
| 94015 | – | CA | 10b | 10a | 1 half zone colder | 64,091 |
| 91702 | – | CA | 10a | 9b | 1 half zone colder | 60,903 |
| 95648 | – | CA | 9b | 9a | 1 half zone colder | 57,459 |
| 84003 | – | UT | 7a | 6a | 2 half zones colder | 57,430 |
| 00987 | – | PR | 13b | 13a | 1 half zone colder | 55,747 |
| 85365 | – | AZ | 10a | 9a | 2 half zones colder | 54,775 |
| 80631 | – | CO | 5b | 5a | 1 half zone colder | 53,722 |
"Near" names the Census place whose centre is closest to the ZIP code area's own Census point, allowing for the place's size, as a rough guide to where the ZIP code is; it is left blank when no place is close enough to name, and only ZIP codes of 20,000 people or more are labelled. A ZIP code is not a city, and a city has many ZIP codes.
What it means for your garden
The USDA's advice is plain: if your zone changed, "it does not mean you should start removing plants from your garden or change what you are growing. What has thrived in your yard will most likely continue to thrive." A zone describes the average coldest night, not the coldest one, so a winter that dips below your band can still kill a plant rated right at the edge. If your ZIP code moved warmer, treat the new zone as room to try a plant rated for it, in a sheltered spot, rather than a promise.
Hardiness zones matter for plants that have to live through winter: perennials, shrubs, fruit trees and bulbs. They say nothing about when to plant tomatoes or beans. Annual vegetables go in after the last spring frost, so for them use your frost dates: our state planting pages quote each state's own planting calendar, the frost dates lookup finds your nearest NOAA station, and the spring planting planner counts back from it. To check your own ZIP code's current zone, use our hardiness zone lookup. Our frost dates study covers the other half of the calendar, state by state.
How we worked it out
The PRISM Group at Oregon State University, which made both maps for the USDA, publishes each map's half zone for every ZIP code. The 2012 lists hold 41,120 ZIP codes and the 2023 lists 40,502. We compared the 40,480 ZIP codes on both lists and left out the 662 that appear on only one (640 only in 2012, 22 only in 2023), since a change can't be measured for them. For each ZIP code we counted the half zones between its two labels, so 6a to 6b is one half zone warmer and 6a to 7a is two, a full zone.
ZIP codes are mail routes, not areas, so the Census Bureau counts people in ZIP Code Tabulation Areas (ZCTAs), which approximate the areas of ZIP codes and carry the same five-digit codes. We joined each ZIP code to the ZCTA with the same code and took that ZCTA's total population from the American Community Survey's 2020-2024 five-year estimates. 99.1% of the 33,772 ZCTAs match a compared ZIP code, covering 99.9% of their population. ZIP codes with no ZCTA, such as post office boxes and single large mailers, count in the ZIP code shares but carry no people. Each ZIP code is counted in the state its first three digits belong to, a split we checked against Census locations; the few ZIP codes and ZCTAs that cross a state line count wholly in that state.
The limits matter. PRISM assigns one half zone to each ZIP code, though a big rural ZIP code can span several on the map itself. The population figures are survey estimates with margins of error, and they describe the 2020s, not 2012. And the change between the two maps mixes a newer thirty-year period, more stations and a better mapping method; the USDA says the 2023 map drew on "data from a total of 13,625 stations—a substantial increase compared to the 2012 map version." None of this can be separated with ZIP code lists alone. This page summarises PRISM's ZIP code listings; it is not the official USDA Plant Hardiness Zone Map. The methodology page explains how we check sources.
Use the data
Journalists, garden writers and Extension educators are welcome to use these figures and the map with credit to Frost and Seed and a link to this page. The state table (CSV) has both the ZIP code and the population shares. To check a number, contact us.
Sources
- PRISM Group, Oregon State University, 2023 USDA Plant Hardiness Zone GIS Datasets: plant hardiness zones by ZIP code (conterminous US, Alaska, Hawaii, Puerto Rico) prism.oregonstate.edu
- PRISM Group, Oregon State University, 2012 USDA Plant Hardiness Zone GIS Datasets: plant hardiness zones by ZIP code prism.oregonstate.edu
- USDA Agricultural Research Service, USDA Plant Hardiness Zone Map: Map Creation planthardiness.ars.usda.gov
- USDA Agricultural Research Service, USDA Plant Hardiness Zone Map: How to Use the Maps planthardiness.ars.usda.gov
- U.S. Census Bureau, American Community Survey 2020-2024 5-year estimates, table B01003 (total population), summary file www2.census.gov
- U.S. Census Bureau, 2024 Gazetteer Files: ZIP Code Tabulation Areas (national file) www2.census.gov
- U.S. Census Bureau, 2024 Gazetteer Files: places (national file) www2.census.gov