Climate zones by state

Oklahoma Climate Zones by County

Oklahoma's 77 counties span climate zones 3A to 4B under the 2021 International Energy Conservation Code (IECC). Zone 3A is the most common, with 59 of the 77. For reference, Oklahoma City and Tulsa are in zone 3A and Guymon is in 4B.

Insulation minimums for each zone in Oklahoma

ZoneCountiesAtticWood-frame wallsFloors over unheated spaceBasement walls
3A59R-49R-20, or 13+5ci, or R-15ciR-19R-5ci or R-13
4A15R-60R-30, or 20+5ci, or 13+10ci, or R-20ciR-19R-10ci or R-13
4B3R-60R-30, or 20+5ci, or 13+10ci, or R-20ciR-19R-10ci or R-13

Minimums from the 2021 IECC (Table R402.1.3). Many areas still enforce an older edition, so check with your local building department. See sources.

Which energy code Oklahoma uses

Oklahoma enforces the 2018 IECC with amendments for homes (in effect since Sep 2022). Next: 2024 IRC, took effect Sep 2026 (DOE still lists it as upcoming). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments. See every state's energy code.

What changed from the 2018 map

In the 2021 map, 15 moved colder: Alfalfa County (3 → 4), Craig County (3 → 4), Delaware County (3 → 4), Ellis County (3 → 4), Garfield County (3 → 4), Grant County (3 → 4), Harper County (3 → 4), Kay County (3 → 4), Major County (3 → 4), Nowata County (3 → 4), Osage County (3 → 4), Ottawa County (3 → 4), and 3 more marked in the table below. If your town still enforces the 2018 or 2015 code, the older zone applies to permits.

Every county in Oklahoma

NameZone (2021)Zone (2018)Details
Adair County3A3AInsulation →
Alfalfa County4A3A changedInsulation →
Atoka County3A3AInsulation →
Beaver County4B4BInsulation →
Beckham County3A3AInsulation →
Blaine County3A3AInsulation →
Bryan County3A3AInsulation →
Caddo County3A3AInsulation →
Canadian County3A3AInsulation →
Carter County3A3AInsulation →
Cherokee County3A3AInsulation →
Choctaw County3A3AInsulation →
Cimarron County4B4BInsulation →
Cleveland County3A3AInsulation →
Coal County3A3AInsulation →
Comanche County3A3AInsulation →
Cotton County3A3AInsulation →
Craig County4A3A changedInsulation →
Creek County3A3AInsulation →
Custer County3A3AInsulation →
Delaware County4A3A changedInsulation →
Dewey County3A3AInsulation →
Ellis County4A3A changedInsulation →
Garfield County4A3A changedInsulation →
Garvin County3A3AInsulation →
Grady County3A3AInsulation →
Grant County4A3A changedInsulation →
Greer County3A3AInsulation →
Harmon County3A3AInsulation →
Harper County4A3A changedInsulation →
Haskell County3A3AInsulation →
Hughes County3A3AInsulation →
Jackson County3A3AInsulation →
Jefferson County3A3AInsulation →
Johnston County3A3AInsulation →
Kay County4A3A changedInsulation →
Kingfisher County3A3AInsulation →
Kiowa County3A3AInsulation →
Latimer County3A3AInsulation →
Le Flore County3A3AInsulation →
Lincoln County3A3AInsulation →
Logan County3A3AInsulation →
Love County3A3AInsulation →
Major County4A3A changedInsulation →
Marshall County3A3AInsulation →
Mayes County3A3AInsulation →
McClain County3A3AInsulation →
McCurtain County3A3AInsulation →
McIntosh County3A3AInsulation →
Murray County3A3AInsulation →
Muskogee County3A3AInsulation →
Noble County3A3AInsulation →
Nowata County4A3A changedInsulation →
Okfuskee County3A3AInsulation →
Oklahoma County3A3AInsulation →
Okmulgee County3A3AInsulation →
Osage County4A3A changedInsulation →
Ottawa County4A3A changedInsulation →
Pawnee County3A3AInsulation →
Payne County3A3AInsulation →
Pittsburg County3A3AInsulation →
Pontotoc County3A3AInsulation →
Pottawatomie County3A3AInsulation →
Pushmataha County3A3AInsulation →
Roger Mills County3A3AInsulation →
Rogers County3A3AInsulation →
Seminole County3A3AInsulation →
Sequoyah County3A3AInsulation →
Stephens County3A3AInsulation →
Texas County4B4BInsulation →
Tillman County3A3AInsulation →
Tulsa County3A3AInsulation →
Wagoner County3A3AInsulation →
Washington County4A3A changedInsulation →
Washita County3A3AInsulation →
Woods County4A3A changedInsulation →
Woodward County4A3A changedInsulation →

Source: Pacific Northwest National Laboratory, Guide to Determining Climate Zone by County: Building America and IECC 2021 Updates (2022).

Frequently asked questions

What climate zone is Oklahoma?

Oklahoma spans IECC climate zones 3A to 4B; zone 3A is the most common. Find your county in the table above, or search by ZIP code.

How much attic insulation do I need in Oklahoma?

In Oklahoma, the 2021 IECC calls for R-49 and R-60 in the attic, depending on the zone. The table near the top of this page lists each zone's minimums.

What energy code does Oklahoma use?

Oklahoma enforces the 2018 IECC with amendments for homes (in effect since Sep 2022). Next: 2024 IRC, took effect Sep 2026 (DOE still lists it as upcoming). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments.

More for Oklahoma: Last frost dates in Oklahoma · Oklahoma planting zones · Frost line depth by state