Missouri climate zones and HVAC design temperatures
Missouri spans 3 IECC climate zones. 95% of people live in zone 4A (mixed, humid). In Kansas City, heating and cooling equipment is sized for 92°F in summer and 9°F in winter.
Design temperatures for major cities
| City | Zone | Summer 1% | Winter 99% | Water in |
|---|---|---|---|---|
| Kansas City | 4A | 92°F | 9°F | 59°F |
| St. Louis | 4A | 93°F | 13°F | 60°F |
| Springfield | 4A | 92°F | 14°F | 60°F |
| Columbia | 4A | 92°F | 10°F | 59°F |
| Joplin | 4A | 94°F | 14°F | 61°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 (Jasper County); coldest winter design: 0°F (Nodaway County).
Typical equipment sizes in Kansas City
One-story house with average insulation (R-13 walls, R-30 attic, double-pane windows), at Kansas City'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 | 2.5 tons + 5 kW backup |
| 2,000 sq ft | 2.5 tons | 40,000 BTU | 3 tons + 8 kW backup |
| 2,500 sq ft | 3.5 tons | 60,000 BTU | 3.5 tons + 8 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 (2 counties, 1% of people)
| County | Summer 1% | Winter 99% |
|---|---|---|
| Dunklin County | 93°F | 22°F |
| Pemiscot County | 93°F | 22°F |
Zone 4A: mixed, humid (87 counties, 95% of people)
| County | Summer 1% | Winter 99% |
|---|---|---|
| Audrain County | 92°F | 10°F |
| Barry County | 91°F | 16°F |
| Barton County | 93°F | 14°F |
| Bates County | 91°F | 10°F |
| Benton County | 91°F | 10°F |
| Bollinger County | 91°F | 16°F |
| Boone County | 92°F | 10°F |
| Buchanan County | 92°F | 6°F |
| Butler County | 92°F | 19°F |
| Caldwell County | 92°F | 6°F |
| Callaway County | 92°F | 10°F |
| Camden County | 91°F | 14°F |
| Cape Girardeau County | 91°F | 16°F |
| Carroll County | 91°F | 9°F |
| Carter County | 92°F | 19°F |
| Cass County | 92°F | 9°F |
| Cedar County | 91°F | 10°F |
| Chariton County | 91°F | 9°F |
| Christian County | 92°F | 14°F |
| Clay County | 93°F | 10°F |
| Clinton County | 91°F | 8°F |
| Cole County | 93°F | 12°F |
| Cooper County | 92°F | 10°F |
| Crawford County | 90°F | 11°F |
| Dade County | 92°F | 14°F |
| Dallas County | 91°F | 14°F |
| Dent County | 91°F | 13°F |
| Douglas County | 91°F | 16°F |
| Franklin County | 91°F | 14°F |
| Gasconade County | 90°F | 11°F |
| Greene County | 92°F | 14°F |
| Henry County | 91°F | 10°F |
| Hickory County | 91°F | 14°F |
| Howard County | 91°F | 9°F |
| Howell County | 91°F | 16°F |
| Iron County | 91°F | 14°F |
| Jackson County | 92°F | 9°F |
| Jasper County | 94°F | 14°F |
| Jefferson County | 93°F | 13°F |
| Johnson County | 91°F | 10°F |
| Laclede County | 91°F | 14°F |
| Lafayette County | 91°F | 10°F |
| Lawrence County | 91°F | 16°F |
| Lincoln County | 93°F | 13°F |
| Madison County | 91°F | 14°F |
| Maries County | 90°F | 11°F |
| McDonald County | 93°F | 18°F |
| Miller County | 91°F | 13°F |
| Mississippi County | 90°F | 17°F |
| Moniteau County | 93°F | 12°F |
| Monroe County | 91°F | 10°F |
| Montgomery County | 91°F | 14°F |
| Morgan County | 91°F | 13°F |
| New Madrid County | 92°F | 19°F |
| Newton County | 94°F | 14°F |
| Oregon County | 91°F | 16°F |
| Osage County | 93°F | 12°F |
| Ozark County | 92°F | 18°F |
| Perry County | 90°F | 13°F |
| Pettis County | 92°F | 10°F |
| Phelps County | 90°F | 11°F |
| Platte County | 91°F | 8°F |
| Polk County | 92°F | 14°F |
| Pulaski County | 91°F | 13°F |
| Randolph County | 92°F | 10°F |
| Ray County | 92°F | 9°F |
| Reynolds County | 91°F | 14°F |
| Ripley County | 92°F | 19°F |
| Saline County | 91°F | 9°F |
| Scott County | 91°F | 16°F |
| Shannon County | 91°F | 16°F |
| St. Charles County | 92°F | 12°F |
| St. Clair County | 91°F | 10°F |
| St. Francois County | 91°F | 14°F |
| St. Louis city | 93°F | 13°F |
| St. Louis County | 94°F | 13°F |
| Ste. Genevieve County | 91°F | 14°F |
| Stoddard County | 92°F | 19°F |
| Stone County | 91°F | 16°F |
| Taney County | 91°F | 16°F |
| Texas County | 91°F | 13°F |
| Vernon County | 93°F | 14°F |
| Warren County | 91°F | 14°F |
| Washington County | 91°F | 14°F |
| Wayne County | 92°F | 19°F |
| Webster County | 92°F | 14°F |
| Wright County | 91°F | 16°F |
Zone 5A: cool, humid (26 counties, 4% of people)
| County | Summer 1% | Winter 99% |
|---|---|---|
| Adair County | 90°F | 4°F |
| Andrew County | 92°F | 6°F |
| Atchison County | 91°F | 1°F |
| Clark County | 90°F | 3°F |
| Daviess County | 92°F | 6°F |
| DeKalb County | 92°F | 6°F |
| Gentry County | 92°F | 6°F |
| Grundy County | 92°F | 6°F |
| Harrison County | 89°F | 2°F |
| Holt County | 92°F | 4°F |
| Knox County | 90°F | 4°F |
| Lewis County | 90°F | 5°F |
| Linn County | 92°F | 6°F |
| Livingston County | 92°F | 6°F |
| Macon County | 90°F | 4°F |
| Marion County | 91°F | 10°F |
| Mercer County | 89°F | 2°F |
| Nodaway County | 90°F | 0°F |
| Pike County | 90°F | 8°F |
| Putnam County | 90°F | 1°F |
| Ralls County | 91°F | 10°F |
| Schuyler County | 90°F | 1°F |
| Scotland County | 90°F | 4°F |
| Shelby County | 91°F | 10°F |
| Sullivan County | 90°F | 4°F |
| Worth County | 89°F | 2°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.