Arkansas climate zones and HVAC design temperatures
Arkansas spans 2 IECC climate zones. 76% of people live in zone 3A (warm, humid). In Little Rock, heating and cooling equipment is sized for 95°F in summer and 25°F in winter.
Design temperatures for major cities
| City | Zone | Summer 1% | Winter 99% | Water in |
|---|---|---|---|---|
| Little Rock | 3A | 95°F | 25°F | 66°F |
| Fayetteville | 4A | 92°F | 17°F | 61°F |
| Fort Smith | 3A | 96°F | 23°F | 65°F |
| Springdale | 4A | 92°F | 17°F | 61°F |
| Jonesboro | 3A | 93°F | 21°F | 64°F |
Summer: exceeded in 1% of hours. Winter: colder in only 1% of hours. Water in: estimated groundwater temperature for tankless water heater sizing. Computed for each county from NOAA hourly weather data, 2015-2024; see where our numbers come from. Hottest summer design in the state: 97°F (Calhoun County); coldest winter design: 16°F (Carroll County).
Typical equipment sizes in Little Rock
One-story house with average insulation (R-13 walls, R-30 attic, double-pane windows), at Little Rock's design temperatures. Your house can need more or less; use the calculators for yours.
| House | Central AC | Gas furnace (95% AFUE) | Heat pump |
|---|---|---|---|
| 1,500 sq ft | 2.5 tons | 40,000 BTU | 2.5 tons + 5 kW backup |
| 2,000 sq ft | 3 tons | 40,000 BTU | 3 tons + 5 kW backup |
| 2,500 sq ft | 3.5 tons | 40,000 BTU | 3.5 tons + 5 kW backup |
AC size calculator Furnace size calculator Heat pump size calculator
Climate zone by county
From the 2021 International Energy Conservation Code (IECC), as published by the U.S. Department of Energy. The zone sets the insulation and window requirements in the energy code; the number runs from 1 (hottest) to 8 (coldest), and the letter is A for moist, B for dry and C for marine.
Zone 3A: warm, humid (63 counties, 76% of people)
| County | Summer 1% | Winter 99% |
|---|---|---|
| Arkansas County | 94°F | 25°F |
| Ashley County | 95°F | 28°F |
| Bradley County | 95°F | 26°F |
| Calhoun County | 97°F | 25°F |
| Chicot County | 95°F | 27°F |
| Clark County | 95°F | 25°F |
| Clay County | 92°F | 19°F |
| Cleburne County | 93°F | 19°F |
| Cleveland County | 95°F | 25°F |
| Columbia County | 95°F | 26°F |
| Conway County | 95°F | 23°F |
| Craighead County | 93°F | 21°F |
| Crawford County | 96°F | 23°F |
| Crittenden County | 93°F | 22°F |
| Cross County | 93°F | 22°F |
| Dallas County | 97°F | 25°F |
| Desha County | 95°F | 26°F |
| Drew County | 95°F | 26°F |
| Faulkner County | 95°F | 22°F |
| Franklin County | 96°F | 23°F |
| Garland County | 96°F | 25°F |
| Grant County | 95°F | 25°F |
| Greene County | 93°F | 21°F |
| Hempstead County | 97°F | 28°F |
| Hot Spring County | 96°F | 25°F |
| Howard County | 96°F | 24°F |
| Independence County | 93°F | 21°F |
| Jackson County | 94°F | 22°F |
| Jefferson County | 95°F | 25°F |
| Johnson County | 95°F | 23°F |
| Lafayette County | 97°F | 28°F |
| Lawrence County | 93°F | 20°F |
| Lee County | 93°F | 23°F |
| Lincoln County | 95°F | 25°F |
| Little River County | 97°F | 28°F |
| Logan County | 96°F | 23°F |
| Lonoke County | 95°F | 22°F |
| Miller County | 97°F | 28°F |
| Mississippi County | 93°F | 22°F |
| Monroe County | 94°F | 25°F |
| Montgomery County | 95°F | 23°F |
| Nevada County | 95°F | 25°F |
| Ouachita County | 97°F | 25°F |
| Perry County | 95°F | 23°F |
| Phillips County | 95°F | 28°F |
| Pike County | 95°F | 23°F |
| Poinsett County | 93°F | 21°F |
| Polk County | 95°F | 24°F |
| Pope County | 95°F | 23°F |
| Prairie County | 94°F | 25°F |
| Pulaski County | 95°F | 25°F |
| Randolph County | 93°F | 20°F |
| Saline County | 95°F | 25°F |
| Scott County | 95°F | 24°F |
| Sebastian County | 96°F | 23°F |
| Sevier County | 96°F | 24°F |
| Sharp County | 93°F | 21°F |
| St. Francis County | 93°F | 22°F |
| Union County | 95°F | 26°F |
| Van Buren County | 93°F | 19°F |
| White County | 94°F | 22°F |
| Woodruff County | 94°F | 22°F |
| Yell County | 95°F | 23°F |
Zone 4A: mixed, humid (12 counties, 24% of people)
| County | Summer 1% | Winter 99% |
|---|---|---|
| Baxter County | 92°F | 18°F |
| Benton County | 91°F | 17°F |
| Boone County | 91°F | 17°F |
| Carroll County | 91°F | 16°F |
| Fulton County | 91°F | 16°F |
| Izard County | 93°F | 21°F |
| Madison County | 92°F | 17°F |
| Marion County | 93°F | 18°F |
| Newton County | 91°F | 17°F |
| Searcy County | 93°F | 19°F |
| Stone County | 93°F | 19°F |
| Washington County | 92°F | 17°F |
Climate data as of 2026-10. Design temperatures may differ by a few degrees from the ACCA Manual J tables your contractor uses; winter values run a little warmer because recent winters have been milder.