North Carolina climate zones and HVAC design temperatures
North Carolina spans 3 IECC climate zones. 89% of people live in zone 3A (warm, humid). In Charlotte, heating and cooling equipment is sized for 93°F in summer and 27°F in winter.
Design temperatures for major cities
| City | Zone | Summer 1% | Winter 99% | Water in |
|---|---|---|---|---|
| Charlotte | 3A | 93°F | 27°F | 65°F |
| Raleigh | 3A | 93°F | 25°F | 64°F |
| Greensboro | 3A | 90°F | 23°F | 62°F |
| Wilmington | 3A | 92°F | 29°F | 67°F |
| Asheville | 4A | 86°F | 21°F | 60°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: 94°F (Bladen County); coldest winter design: 16°F (Surry County).
Typical equipment sizes in Charlotte
One-story house with average insulation (R-13 walls, R-30 attic, double-pane windows), at Charlotte'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 |
| 2,000 sq ft | 3 tons | 40,000 BTU | 3 tons |
| 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 (79 counties, 89% of people)
| County | Summer 1% | Winter 99% |
|---|---|---|
| Alamance County | 92°F | 23°F |
| Alexander County | 90°F | 24°F |
| Anson County | 93°F | 27°F |
| Beaufort County | 91°F | 27°F |
| Bertie County | 91°F | 22°F |
| Bladen County | 94°F | 27°F |
| Brunswick County | 92°F | 29°F |
| Cabarrus County | 91°F | 27°F |
| Camden County | 91°F | 26°F |
| Carteret County | 87°F | 30°F |
| Caswell County | 91°F | 22°F |
| Catawba County | 90°F | 24°F |
| Chatham County | 92°F | 23°F |
| Cherokee County | 91°F | 22°F |
| Chowan County | 91°F | 26°F |
| Clay County | 93°F | 29°F |
| Cleveland County | 92°F | 26°F |
| Columbus County | 88°F | 30°F |
| Craven County | 91°F | 27°F |
| Cumberland County | 93°F | 26°F |
| Currituck County | 91°F | 26°F |
| Dare County | 89°F | 30°F |
| Davidson County | 90°F | 24°F |
| Davie County | 90°F | 24°F |
| Duplin County | 92°F | 25°F |
| Durham County | 93°F | 25°F |
| Edgecombe County | 93°F | 25°F |
| Forsyth County | 90°F | 24°F |
| Franklin County | 93°F | 25°F |
| Gaston County | 92°F | 26°F |
| Gates County | 91°F | 24°F |
| Granville County | 93°F | 25°F |
| Greene County | 93°F | 27°F |
| Guilford County | 90°F | 23°F |
| Halifax County | 91°F | 22°F |
| Harnett County | 93°F | 26°F |
| Hertford County | 91°F | 22°F |
| Hoke County | 93°F | 26°F |
| Hyde County | 87°F | 32°F |
| Iredell County | 91°F | 27°F |
| Johnston County | 93°F | 27°F |
| Jones County | 91°F | 27°F |
| Lee County | 93°F | 24°F |
| Lenoir County | 93°F | 27°F |
| Lincoln County | 92°F | 26°F |
| Martin County | 93°F | 25°F |
| Mecklenburg County | 93°F | 27°F |
| Montgomery County | 93°F | 24°F |
| Moore County | 93°F | 24°F |
| Nash County | 93°F | 25°F |
| New Hanover County | 92°F | 29°F |
| Northampton County | 91°F | 22°F |
| Onslow County | 90°F | 28°F |
| Orange County | 93°F | 25°F |
| Pamlico County | 91°F | 29°F |
| Pasquotank County | 91°F | 26°F |
| Pender County | 92°F | 29°F |
| Perquimans County | 91°F | 26°F |
| Person County | 91°F | 22°F |
| Pitt County | 93°F | 25°F |
| Polk County | 86°F | 21°F |
| Randolph County | 90°F | 23°F |
| Richmond County | 92°F | 26°F |
| Robeson County | 94°F | 27°F |
| Rockingham County | 90°F | 19°F |
| Rowan County | 91°F | 27°F |
| Rutherford County | 91°F | 28°F |
| Sampson County | 94°F | 27°F |
| Scotland County | 94°F | 27°F |
| Stanly County | 91°F | 27°F |
| Tyrrell County | 91°F | 26°F |
| Union County | 92°F | 26°F |
| Vance County | 90°F | 22°F |
| Wake County | 93°F | 25°F |
| Warren County | 90°F | 22°F |
| Washington County | 91°F | 26°F |
| Wayne County | 93°F | 27°F |
| Wilkes County | 88°F | 21°F |
| Wilson County | 93°F | 25°F |
Zone 4A: mixed, humid (16 counties, 9% of people)
| County | Summer 1% | Winter 99% |
|---|---|---|
| Buncombe County | 86°F | 21°F |
| Burke County | 90°F | 24°F |
| Caldwell County | 90°F | 24°F |
| Graham County | 91°F | 22°F |
| Haywood County | 86°F | 21°F |
| Henderson County | 86°F | 21°F |
| Jackson County | 86°F | 21°F |
| Macon County | 93°F | 29°F |
| Madison County | 86°F | 21°F |
| McDowell County | 86°F | 21°F |
| Mitchell County | 81°F | 17°F |
| Stokes County | 90°F | 24°F |
| Surry County | 82°F | 16°F |
| Swain County | 91°F | 22°F |
| Transylvania County | 86°F | 21°F |
| Yadkin County | 88°F | 21°F |
Zone 5A: cool, humid (5 counties, 1% of people)
| County | Summer 1% | Winter 99% |
|---|---|---|
| Alleghany County | 88°F | 21°F |
| Ashe County | 81°F | 17°F |
| Avery County | 81°F | 17°F |
| Watauga County | 81°F | 17°F |
| Yancey County | 86°F | 21°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.