Set the thermostat between 78 and 82°F, put the fan on auto, and leave the system on — that’s the consensus across Florida HVAC guides for an unoccupied home. Never turn the AC off: in most Florida houses it’s the only dehumidifier you have, and the real target isn’t a temperature at all — it’s indoor humidity below 60%.
Why “off” is the one wrong answer
Turning the AC off before a trip feels like the frugal move. In Ohio it is. In South Florida it’s how you come home to musty closets, a damp-smelling sofa, and grout that darkened while you were gone. A sealed house stops exchanging air, outdoor humidity works its way in anyway, and with the AC off nothing removes that moisture. During the rainy season — roughly June through November — a closed Miami home can drift into sustained high humidity within days of the system going quiet.
The number that matters here is the EPA’s published guidance: keep indoor relative humidity below 60%, ideally 30–50%. We’ve written a full explainer on what that humidity band means in a Miami home — the short version is that in most homes the air conditioner is the only machine holding you inside it.
Why 78–82°F, and why the fan setting matters as much
The 78–82°F range that Florida HVAC companies broadly recommend for vacant homes is a compromise with a logic to it: warm enough that you’re not paying to fully cool an empty house, cool enough that the system still cycles regularly — and every cooling cycle pulls moisture out of the air as a side effect. Set it to 85°F+ and the system may barely run at all, which quietly turns “on” into “off.”
Two settings decide whether those cycles actually dry the house:
- Fan on AUTO, never ON. On “auto,” the fan runs only while cooling, and the moisture condensed on the cold coil drains away. On “on,” the fan keeps blowing between cycles — across a wet coil — and re-evaporates that moisture straight back into your rooms.
- A humidistat, if you have one. Many Florida systems can hold a humidity setpoint directly. Around 60% for a vacant home does the real job better than any temperature number, because humidity is the thing you were using temperature to approximate.
If your thermostat is smart, use it: a remote temperature-and-humidity readout is the difference between guessing and knowing. A standalone Wi-Fi hygrometer costs little and answers the “is the house okay?” question from 1,200 miles away.
The part the thermostat can’t do
In the homes we open back up after a season away, the difference between “smells fine” and “smells like a closed house” usually isn’t only the thermostat — it’s what was left behind. Humid months settle a film onto surfaces, and whatever organic material sits out — crumbs, spills, a full trash can, produce forgotten in a bowl — becomes the thing that odor and mildew start from. A house that leaves clean comes back better than a house that leaves cooled.
Before you lock the door: empty the refrigerator of anything that can expire, run and empty the dishwasher and washing machine and leave their doors cracked, take out every trash can, and leave interior doors and closets slightly open so conditioned air actually reaches them. Then have someone — a neighbor, a relative, a property watcher — walk the house periodically; an AC failure in week two of a twelve-week absence is only a disaster if nobody notices it.
If you keep a seasonal home here, this pairs with the return trip: we’ve covered whether to book a cleaning before you come back, and why that returning visit is a deep clean rather than a standard one. A closed-up season leaves the kind of settled film that JAS’s deep clean is scoped for — a 4–6 hour visit with a 2-person team, 42 items verified by photo, starting at $349.
Questions about your place specifically? No need to finish the article — call, text, WhatsApp, or email us and we’ll take it from here.
The honest boundaries
Two things this article won’t claim. First, no thermostat setting is a guarantee — 78–82°F with the fan on auto is the well-supported convention, not a certification that nothing can go wrong in a Florida summer. Second, if you return to visible, spreading mold rather than a musty smell and surface film, that’s a remediation situation, not a cleaning: our published terms let us pause service where conditions like mold or infestation make it unsafe, and the right first call is a remediation professional.
FAQ
Should I just turn the AC off to save money while I’m away?
No — not in Florida. The savings on the electric bill are real but small compared to what sustained indoor humidity does to a closed house. The published compromise is 78–82°F: most of the savings, while the system keeps dehumidifying.
Is 82°F too warm? The house feels hot when we get back.
It’s warm for people, fine for an empty house — the setting is about keeping cycles running, not comfort. Use a smart thermostat to drop it to your normal temperature a day before you land.
What if the power goes out while we’re gone?
That’s the strongest argument for monitoring: a Wi-Fi thermostat or hygrometer alerts you when conditions drift, and a local contact can check the house. After any extended outage in the wet season, walk the house — or have someone walk it — before assuming all is well.