2021 IECC
Climate Zones by State and County
The energy code splits the US into eight climate zones, from 1 (Miami, Honolulu) to 8 (interior Alaska), plus a letter for moisture: A humid, B dry, C marine. Your zone sets the minimum insulation the code requires for new homes and additions. Pick your state to see every county.
Alabama2A, 3AAlaska5C – 8Arizona2B – 5BArkansas3A, 4ACalifornia2B – 6BColorado4B – 7Connecticut5ADelaware4ADistrict of Columbia4AFlorida1A, 2AGeorgia2A, 3AHawaii1AIdaho5B, 6BIllinois4A, 5AIndiana4A, 5AIowa5A, 6AKansas4A, 5AKentucky4ALouisiana2A, 3AMaine6A, 7Maryland4A, 5AMassachusetts5AMichigan5A, 6A, 7Minnesota5A, 6A, 7Mississippi2A, 3AMissouri3A, 4A, 5AMontana6BNebraska5ANevada3B, 4B, 5BNew Hampshire5A, 6ANew Jersey4A, 5ANew Mexico3B, 4B, 5BNew York4A, 5A, 6ANorth Carolina3A, 4A, 5ANorth Dakota6A, 7Ohio4A, 5AOklahoma3A, 4A, 4BOregon4C, 5BPennsylvania4A, 5ARhode Island5ASouth Carolina2A, 3ASouth Dakota5A, 6ATennessee3A, 4ATexas1A – 4BUtah3B, 5B, 6BVermont6AVirginia3A, 4A, 5AWashington4C – 6BWest Virginia4A, 5AWisconsin5A, 6AWyoming5B, 6B, 7
What the zone numbers mean
| Zone | Climate | Example places |
|---|---|---|
| 1 | Very hot, humid | Miami, Honolulu |
| 2 | Hot | Houston, Dallas, Phoenix |
| 3 | Warm | Plano (Collin County), Atlanta, Las Vegas, Los Angeles |
| 4 | Mixed | New York City, St. Louis, Albuquerque, Seattle and Portland (4C) |
| 5 | Cool | Chicago, Denver, Boston, Salt Lake City |
| 6 | Cold | Minneapolis, Burlington VT, Fargo, Bozeman |
| 7 | Very cold | Duluth, Anchorage, Jackson WY |
| 8 | Subarctic | Fairbanks and interior Alaska |
Download the data
Want the raw data? Download the CSV file. It has every county, with its zone in 2021 and in 2018. The data comes from a US national lab and the code book. It's free to use. A link back to us helps.