Louisiana climate zones and HVAC design temperatures
Louisiana spans 2 IECC climate zones. 78% of people live in zone 2A (hot, humid). In New Orleans, heating and cooling equipment is sized for 93°F in summer and 40°F in winter.
Design temperatures for major cities
| City | Zone | Summer 1% | Winter 99% | Water in |
|---|---|---|---|---|
| New Orleans | 2A | 93°F | 40°F | 74°F |
| Baton Rouge | 2A | 95°F | 33°F | 71°F |
| Shreveport | 3A | 97°F | 30°F | 70°F |
| Lafayette | 2A | 94°F | 35°F | 72°F |
| Lake Charles | 2A | 94°F | 35°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 parish from NOAA hourly weather data, 2015-2024; see where our numbers come from. Hottest summer design in the state: 97°F (Caddo Parish); coldest winter design: 28°F (Bossier Parish).
Typical equipment sizes in New Orleans
One-story house with average insulation (R-13 walls, R-30 attic, double-pane windows), at New Orleans'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 parish
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 2A: hot, humid (37 parishes, 78% of people)
| Parish | Summer 1% | Winter 99% |
|---|---|---|
| Acadia Parish | 94°F | 35°F |
| Allen Parish | 95°F | 30°F |
| Ascension Parish | 95°F | 33°F |
| Assumption Parish | 95°F | 33°F |
| Avoyelles Parish | 96°F | 29°F |
| Beauregard Parish | 95°F | 32°F |
| Calcasieu Parish | 94°F | 35°F |
| Cameron Parish | 94°F | 35°F |
| East Baton Rouge Parish | 95°F | 33°F |
| East Feliciana Parish | 95°F | 33°F |
| Evangeline Parish | 94°F | 31°F |
| Iberia Parish | 94°F | 34°F |
| Iberville Parish | 95°F | 33°F |
| Jefferson Davis Parish | 94°F | 35°F |
| Jefferson Parish | 94°F | 39°F |
| Lafayette Parish | 94°F | 35°F |
| Lafourche Parish | 93°F | 37°F |
| Livingston Parish | 95°F | 33°F |
| Orleans Parish | 93°F | 40°F |
| Plaquemines Parish | 93°F | 35°F |
| Pointe Coupee Parish | 92°F | 32°F |
| Rapides Parish | 96°F | 30°F |
| St. Bernard Parish | 93°F | 35°F |
| St. Charles Parish | 94°F | 39°F |
| St. Helena Parish | 95°F | 32°F |
| St. James Parish | 94°F | 39°F |
| St. John the Baptist Parish | 94°F | 39°F |
| St. Landry Parish | 94°F | 31°F |
| St. Martin Parish | 94°F | 35°F |
| St. Mary Parish | 94°F | 34°F |
| St. Tammany Parish | 94°F | 32°F |
| Tangipahoa Parish | 95°F | 32°F |
| Terrebonne Parish | 93°F | 37°F |
| Vermilion Parish | 93°F | 33°F |
| Washington Parish | 95°F | 32°F |
| West Baton Rouge Parish | 95°F | 33°F |
| West Feliciana Parish | 92°F | 32°F |
Zone 3A: warm, humid (27 parishes, 22% of people)
| Parish | Summer 1% | Winter 99% |
|---|---|---|
| Bienville Parish | 96°F | 29°F |
| Bossier Parish | 96°F | 28°F |
| Caddo Parish | 97°F | 30°F |
| Caldwell Parish | 96°F | 29°F |
| Catahoula Parish | 93°F | 28°F |
| Claiborne Parish | 96°F | 29°F |
| Concordia Parish | 93°F | 28°F |
| De Soto Parish | 97°F | 30°F |
| East Carroll Parish | 95°F | 28°F |
| Franklin Parish | 96°F | 29°F |
| Grant Parish | 96°F | 30°F |
| Jackson Parish | 95°F | 28°F |
| LaSalle Parish | 96°F | 29°F |
| Lincoln Parish | 95°F | 28°F |
| Madison Parish | 95°F | 28°F |
| Morehouse Parish | 95°F | 28°F |
| Natchitoches Parish | 97°F | 29°F |
| Ouachita Parish | 96°F | 29°F |
| Red River Parish | 97°F | 29°F |
| Richland Parish | 96°F | 29°F |
| Sabine Parish | 95°F | 30°F |
| Tensas Parish | 93°F | 28°F |
| Union Parish | 95°F | 28°F |
| Vernon Parish | 95°F | 31°F |
| Webster Parish | 96°F | 29°F |
| West Carroll Parish | 95°F | 28°F |
| Winn Parish | 97°F | 29°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.