Florida climate zones and HVAC design temperatures
Florida spans 2 IECC climate zones. 71% of people live in zone 2A (hot, humid). In Jacksonville, heating and cooling equipment is sized for 94°F in summer and 42°F in winter.
Design temperatures for major cities
| City | Zone | Summer 1% | Winter 99% | Water in |
|---|---|---|---|---|
| Jacksonville | 2A | 94°F | 42°F | 75°F |
| Miami | 1A | 92°F | 56°F | 80°F |
| Tampa | 2A | 95°F | 41°F | 75°F |
| Orlando | 2A | 93°F | 46°F | 76°F |
| Tallahassee | 2A | 95°F | 33°F | 72°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 (Baker County); coldest winter design: 32°F (Baker County).
Typical equipment sizes in Jacksonville
One-story house with average insulation (R-13 walls, R-30 attic, double-pane windows), at Jacksonville'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 |
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 1A: very hot, humid (4 counties, 29% of people)
| County | Summer 1% | Winter 99% |
|---|---|---|
| Broward County | 92°F | 53°F |
| Miami-Dade County | 92°F | 56°F |
| Monroe County | 92°F | 60°F |
| Palm Beach County | 91°F | 52°F |
Zone 2A: hot, humid (63 counties, 71% of people)
| County | Summer 1% | Winter 99% |
|---|---|---|
| Alachua County | 93°F | 36°F |
| Baker County | 97°F | 32°F |
| Bay County | 91°F | 38°F |
| Bradford County | 93°F | 36°F |
| Brevard County | 90°F | 51°F |
| Calhoun County | 94°F | 33°F |
| Charlotte County | 93°F | 46°F |
| Citrus County | 91°F | 36°F |
| Clay County | 97°F | 32°F |
| Collier County | 92°F | 51°F |
| Columbia County | 93°F | 36°F |
| DeSoto County | 93°F | 46°F |
| Dixie County | 93°F | 33°F |
| Duval County | 94°F | 42°F |
| Escambia County | 93°F | 37°F |
| Flagler County | 91°F | 43°F |
| Franklin County | 91°F | 37°F |
| Gadsden County | 95°F | 33°F |
| Gilchrist County | 93°F | 33°F |
| Glades County | 91°F | 43°F |
| Gulf County | 91°F | 38°F |
| Hamilton County | 94°F | 33°F |
| Hardee County | 94°F | 46°F |
| Hendry County | 92°F | 49°F |
| Hernando County | 93°F | 38°F |
| Highlands County | 91°F | 43°F |
| Hillsborough County | 95°F | 41°F |
| Holmes County | 95°F | 32°F |
| Indian River County | 91°F | 46°F |
| Jackson County | 94°F | 33°F |
| Jefferson County | 91°F | 34°F |
| Lafayette County | 93°F | 33°F |
| Lake County | 93°F | 43°F |
| Lee County | 93°F | 50°F |
| Leon County | 95°F | 33°F |
| Levy County | 93°F | 37°F |
| Liberty County | 95°F | 33°F |
| Madison County | 94°F | 33°F |
| Manatee County | 92°F | 47°F |
| Marion County | 93°F | 37°F |
| Martin County | 91°F | 45°F |
| Nassau County | 93°F | 36°F |
| Okaloosa County | 92°F | 34°F |
| Okeechobee County | 91°F | 43°F |
| Orange County | 93°F | 46°F |
| Osceola County | 93°F | 45°F |
| Pasco County | 93°F | 38°F |
| Pinellas County | 92°F | 48°F |
| Polk County | 94°F | 46°F |
| Putnam County | 93°F | 36°F |
| Santa Rosa County | 93°F | 37°F |
| Sarasota County | 91°F | 48°F |
| Seminole County | 93°F | 44°F |
| St. Johns County | 90°F | 41°F |
| St. Lucie County | 91°F | 45°F |
| Sumter County | 93°F | 43°F |
| Suwannee County | 93°F | 33°F |
| Taylor County | 93°F | 33°F |
| Union County | 93°F | 36°F |
| Volusia County | 91°F | 43°F |
| Wakulla County | 95°F | 33°F |
| Walton County | 92°F | 40°F |
| Washington County | 95°F | 32°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.