In Louisiana, March is as close to an off-switch as the year gets, and even that pause is partial. At roughly 200 combined heating and cooling degree days, March asks the house for less than any other month, but it never asks for nothing. This guide walks through both changeovers, plus the stretch of days, mainly in March and November, when the same 24 hours can call for heat before breakfast and air conditioning by mid-afternoon.
The quietest month in Louisiana
March is the calmest month on the calendar here, with about 200 heating and cooling degree days combined. That number needs context to mean anything: nationally, the mildest month in any state runs from about 70 degree days at the low end to about 246 at the high end. Louisiana’s 200 sits well up in that range, closer to the states that never really get a break than to the ones that do.
Degree days measure demand, not temperature. A day with 20 heating degree days isn’t a temperature reading; it’s a way of saying how much work a furnace or heat pump had to do to keep the house at a standard indoor comfort level. The higher the number, the harder the equipment worked, whether that work was heating or cooling.
So what does 200 in March actually mean for a Louisiana household? It means March is not a true dead zone. Some mornings still call for a few minutes of heat, and some afternoons already pull enough sun and humidity to want a little cooling. This is a changeover month, not an off month. The shape of the year here runs from a winter with real, sustained heating demand, into a short, quick spring, straight into a long, heavy-humidity summer that dominates the degree-day ledger, then back down through a mild autumn that starts to ask for heat again before winter fully sets in. There’s no stretch where the thermostat can simply be forgotten. The honest answer for Louisiana isn’t “here’s your two-week window to shut everything off.” It’s that the equipment cycles down gradually, and the two real events worth planning around are the shutdown at the end of the heating season and the startup at the beginning of the cooling season, both of which land in that same shoulder territory around March and, on the other side of the year, around November.
Shutting the heat down for the year
The transition out of heating season isn’t a single afternoon; it’s a short sequence, done in order, usually sometime in spring as temperatures climb back toward that 65°F baseline NOAA uses to count heating degree days.
- Stop calling for heat at the thermostat first, rather than cutting power at the breaker or shutting off fuel at the source. Let the system respond to the setting, not to a hard interruption.
- Let the system finish whatever cycle it’s mid-way through before touching anything else. A furnace or heat pump stopped mid-cycle is more likely to trip a fault code than one allowed to shut down on its own.
- For any fuel-burning equipment, follow the manufacturer’s guidance on shutdown and pilot operation. This isn’t a routine homeowner task on modern equipment, and the manufacturer’s instructions govern it, not a general checklist.
- Inspect, clean, or change the filter. ENERGY STAR is explicit on this: “Inspect, clean, or change air filters once a month in your central air conditioner, furnace, and/or heat pump.” That’s monthly, for all three types of equipment, not just the furnace.
- If a humidifier is mounted on the ductwork, shut it down and close its damper. It’s the single most commonly forgotten step in this whole sequence, because it’s out of sight and doesn’t have its own thermostat.
- Clear vents and registers of anything that accumulated over winter, and give the equipment area a quick visual check for dust, debris, or anything stored too close to it.
Louisiana’s heating season runs roughly five months, November through March, and by the time this shutdown sequence happens, heating degree days have already dropped to near nothing (27 in April, 1 in May). There’s no case here for worrying about frozen plumbing from an early shutdown; the caution that applies in colder states doesn’t really bite in Louisiana, because the season has already turned before anyone’s contemplating flipping the system off.
The first run of the cooling season
The best day to test the air conditioner for the first time isn’t the first 90-degree day. It’s a mild one, weeks earlier, when a problem can be diagnosed and fixed calmly instead of discovered while the house is already uncomfortable and every repair company in town is booked solid.
- Clear the outdoor unit of leaves, grass clippings, or anything piled against it over the cooler months.
- Check the condensate drain path for clogs; a blocked line is one of the most common causes of water damage from a system that otherwise runs fine.
- Change or wash the filter. ENERGY STAR’s other maintenance figure applies directly here: “Airflow problems can reduce your system’s efficiency by up to 15 percent.” A dirty filter is the cheapest, fastest way to lose that efficiency for no visible reason.
- Run the system in COOL for a full cycle on a mild day, not a hot one, so a fault shows up while there’s still time to schedule a fix.
- Feel the air at a register far from the equipment, not the closest one. Weak airflow at the far end of the house shows up before it shows up anywhere near the unit itself.
How much of this applies depends on what’s actually installed. In Louisiana, 93% of homes run some form of air conditioning, and 76% run a central system, meaning the outdoor-unit and condensate checks above apply to most households directly. The remaining share, on window units, portables, or ductless mini-splits, skips the outdoor-condenser and condensate steps and focuses mainly on the filter and airflow. Ceiling fans, found in 87% of homes here, aren’t a substitute for any of this, but running them alongside the first cool days can stretch comfort a little further before the AC needs to carry the full load.
The days that ask for both
March and November are the two months here that qualify as asking for both heat and cooling in the same stretch: at least 50 heating degree days and at least 50 cooling degree days in the month. That threshold isn’t a NOAA category; it’s a convention stated here to describe a real pattern, not a line drawn by the agency. March runs 118 heating and 81 cooling degree days; November runs 143 and 66. Both mean a house that wants heat some mornings and cooling some afternoons, in the same week, sometimes the same day.
This is where thermostat settings matter more than usual. A narrow gap between the heating and cooling setpoints is the expensive mistake: the house heats in the morning, then spends the afternoon cooling the same air it just paid to warm up.
| Approach | What it does | Cost or caution | Best use |
|---|---|---|---|
| AUTO changeover | Thermostat switches between heat and cool automatically as the temperature crosses each setpoint | Convenient, but can short-cycle between modes if setpoints are too close together | Homes that want minimal manual adjustment during shoulder months |
| Wide deadband | A gap of several degrees between the heating and cooling setpoints, so neither system fires unless it’s actually needed | No extra cost; just a setting change | Almost every Louisiana household in March or November |
| Manual switching | Homeowner changes the system mode by hand as conditions shift | Requires attention; easy to forget and leave the wrong mode running overnight | Homes without AUTO mode available |
| Open windows | No equipment runs at all; natural ventilation covers the mild stretch | Free, but only works on the calmer days within these months | Mornings and evenings in March and November when neither heat nor cooling degree days are climbing fast |
And the changeover in the other direction
Heating demand starts building again in November, the first month whose average temperature falls back under the 65°F baseline NOAA uses to count heating degree days. It climbs through the winter, peaking in January at 350 degree days, and holds through about five months before easing off again in April.
What that pre-season check should focus on depends on what’s actually installed. In Louisiana, 57% of homes run a furnace and 21% run a central heat pump, with electricity as the dominant heating fuel at 62% of homes and natural gas at 33%. Steam or hot-water boilers and fuel oil systems aren’t reported in enough numbers here to publish a figure, which means the survey found too few households running them to report reliably, not that none exist. That makes this mostly a furnace-and-heat-pump state: a fall checklist here should center on filter changes, heat pump defrost and outdoor coil clearance, and thermostat mode, not on bleeding radiators or checking boiler pressure. The full autumn sequence, covering exactly those furnace and heat pump specifics, belongs in the heating-season guide on this site, and November, with its mean temperature already dipping below that 65°F line, is the right time to go find it.