West Virginia climate zones and HVAC design temperatures
West Virginia spans 2 IECC climate zones. 69% of people live in zone 4A (mixed, humid). In Charleston, heating and cooling equipment is sized for 89°F in summer and 16°F in winter.
Design temperatures for major cities
| City | Zone | Summer 1% | Winter 99% | Water in |
|---|---|---|---|---|
| Charleston | 4A | 89°F | 16°F | 59°F |
| Huntington | 4A | 89°F | 15°F | 59°F |
| Morgantown | 5A | 88°F | 13°F | 57°F |
| Parkersburg | 4A | 88°F | 12°F | 57°F |
| Wheeling | 5A | 86°F | 11°F | 56°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: 90°F (Barbour County); coldest winter design: 9°F (Grant County).
Typical equipment sizes in Charleston
One-story house with average insulation (R-13 walls, R-30 attic, double-pane windows), at Charleston'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 tons | 40,000 BTU | 2 tons + 5 kW backup |
| 2,000 sq ft | 2.5 tons | 40,000 BTU | 3 tons + 5 kW backup |
| 2,500 sq ft | 3 tons | 60,000 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 4A: mixed, humid (36 counties, 69% of people)
| County | Summer 1% | Winter 99% |
|---|---|---|
| Berkeley County | 89°F | 16°F |
| Boone County | 89°F | 16°F |
| Braxton County | 90°F | 10°F |
| Cabell County | 89°F | 15°F |
| Calhoun County | 88°F | 12°F |
| Clay County | 89°F | 16°F |
| Doddridge County | 88°F | 13°F |
| Fayette County | 83°F | 12°F |
| Gilmer County | 90°F | 10°F |
| Greenbrier County | 84°F | 13°F |
| Jackson County | 89°F | 16°F |
| Jefferson County | 89°F | 16°F |
| Kanawha County | 89°F | 16°F |
| Lewis County | 90°F | 10°F |
| Lincoln County | 89°F | 16°F |
| Logan County | 88°F | 17°F |
| Mason County | 89°F | 11°F |
| McDowell County | 81°F | 13°F |
| Mercer County | 81°F | 13°F |
| Mingo County | 86°F | 17°F |
| Monroe County | 86°F | 17°F |
| Morgan County | 89°F | 16°F |
| Nicholas County | 84°F | 13°F |
| Pleasants County | 88°F | 12°F |
| Putnam County | 89°F | 16°F |
| Raleigh County | 83°F | 12°F |
| Ritchie County | 88°F | 12°F |
| Roane County | 89°F | 16°F |
| Summers County | 83°F | 12°F |
| Tyler County | 88°F | 12°F |
| Upshur County | 90°F | 10°F |
| Wayne County | 89°F | 15°F |
| Webster County | 90°F | 10°F |
| Wirt County | 88°F | 12°F |
| Wood County | 88°F | 12°F |
| Wyoming County | 83°F | 12°F |
Zone 5A: cool, humid (19 counties, 31% of people)
| County | Summer 1% | Winter 99% |
|---|---|---|
| Barbour County | 90°F | 10°F |
| Brooke County | 86°F | 11°F |
| Grant County | 85°F | 9°F |
| Hampshire County | 88°F | 18°F |
| Hancock County | 87°F | 10°F |
| Hardy County | 90°F | 18°F |
| Harrison County | 88°F | 13°F |
| Marion County | 88°F | 13°F |
| Marshall County | 86°F | 11°F |
| Mineral County | 88°F | 18°F |
| Monongalia County | 88°F | 13°F |
| Ohio County | 86°F | 11°F |
| Pendleton County | 85°F | 9°F |
| Pocahontas County | 79°F | 9°F |
| Preston County | 88°F | 13°F |
| Randolph County | 85°F | 9°F |
| Taylor County | 88°F | 13°F |
| Tucker County | 85°F | 9°F |
| Wetzel County | 88°F | 13°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.