How do you get through a heat wave without AC?

You cool the person, then the house, and in that order. The body sheds heat by evaporating sweat, so the useful moves are the ones that help water leave skin: a cool shower, a wet towel on the neck and forearms, loose clothing, and moving air across damp skin rather than dry skin. Then the building: shut it up before the outside air passes the inside temperature, blinds down on the sunny side, and open everything once the outside air has dropped back below. Pick one room and defend it instead of the whole home. And know where the nearest air-conditioned public building is, because a few hours there does more than anything you own.

Do fans actually help in extreme heat?

They help until the air gets hot enough that they stop, and the switchover is invisible. A fan does not cool air, it moves it, and what it buys you is faster evaporation from skin. Once the air is hotter than your skin, moving more of it over you adds heat rather than removing it, and if the humidity is high enough that sweat is not evaporating, the fan has nothing left to work with. Ready.gov puts it bluntly: fans create air flow and a false sense of comfort, but do not reduce body temperature or prevent heat-related illnesses. The CDC's version is the same — do not rely solely on fans to keep you cool.

What is the heat index and why is it higher than the temperature?

The heat index is how hot it feels once relative humidity is combined with the air temperature, and it is higher because humid air makes your own cooling system work worse. Sweat only cools you when it evaporates, and it evaporates slowly into air that is already carrying water. The number moves a long way: 92 °F at 45 percent humidity reads 96 °F on the National Weather Service chart, and the same 92 °F at 80 percent humidity reads 121 °F. The chart is also built for shade and light wind, and the NWS says full sunshine can add up to 15 °F on top.

How much water should you drink during a heat wave?

More than thirst asks for, and steadily rather than in one go, because thirst lags behind what the body has already lost. The practical version is a bottle within reach that you refill on a schedule, and drinking on the clock rather than when you notice. Keep the household's stored water topped up too: the standard planning figure is one gallon per person per day, and heat is exactly the situation where that figure is a floor. Anyone on a fluid restriction, a diuretic, or medication for blood pressure or the heart has a different answer, and the person who gives it is their doctor or pharmacist, not a website.

What do I do if the power goes out during a heat wave?

Treat it as a clock, not an inconvenience. Without power the house keeps absorbing heat and stops being able to shed any, the fans stop, and in a tall building the water can stop as well. Fill containers early, keep the refrigerator and freezer shut, and move to the coolest room. Then make the call most households postpone too long: if anyone in the house is over 65, under two, pregnant, on a daily medication that affects heat tolerance, or dependent on a powered medical device, they leave for an air-conditioned place rather than waiting for the grid. A battery will run fans, phones and a radio. It will not run air conditioning.

What are the signs of heat stroke?

Ready.gov describes an extremely high body temperature, above 103 °F, along with red, hot and dry skin with no sweat, and that combination is a 911 call made immediately, not a reason to try something at home first. Confusion, slurred speech, staggering, fainting or a person who has stopped making sense are the same emergency. Nothing on this page treats any of that — no wet towel, no cool shower, no glass of water is a treatment, and improvising one costs the minutes that matter. Call 911, say the person has been in the heat, and follow the instructions the dispatcher gives you while help is on the way.

Heat Wave Without AC: How to Get Through It at Home

Ninety-two degrees.

That number can mean two entirely different afternoons. At 45 percent humidity the National Weather Service chart reads it as 96 °F and files it under Extreme Caution. At 80 percent humidity, the same 92 °F reads 121 °F and sits in Danger. Nothing moved on the thermometer. What moved was the air’s willingness to take your sweat.

Which is the whole problem with a heat wave without AC, and the reason most advice about it aims at the wrong object. People try to cool a house. A house is tons of drywall and furniture that soaked up sun all day and hands it back all night, and you will not win that. What you can cool, cheaply and in four minutes, is a person.

Most American homes do have air conditioning, so the case that actually catches households is not a home without a unit. It is the afternoon the unit stops — a failed compressor, a landlord who will not come, a grid that goes down in the worst week of July. Ready.gov is blunt about the stakes: extreme heat is responsible for the highest number of annual deaths among all weather-related hazards. Not the wind, not the water.

The short version

A heat wave without AC is handled person first, house second. Cool the person: water on skin with air moving over it, loose clothes, a cool shower, drinking on a schedule rather than on thirst. Know the fan rule — a fan only speeds evaporation, and Ready.gov says fans do not prevent heat-related illness. Shut the house before the outside air passes the inside, blinds down on the sunny side, and flush it once that air drops back below. Defend one room, not the whole home. Read the alert: a warning is dangerous heat expected or occurring, an advisory sits below it, and thresholds are local. Go somewhere cooled for a few hours — a library, a mall, a county cooling center — because that beats anything on this page. A thermometer that also reads humidity^aff. tells you which of these you need today. And if the power is out too, the extended power outage clock starts at the same moment.

Same 92 °F, humidity 45 % then 80 %: 96 → 121 °F
What full sunshine adds: +15 °F
Body temperature: call 911: 103 °F

Your body sheds heat by evaporating water, and humidity is what stops it

Four routes carry heat out of a person: radiation, conduction, convection and evaporation. On an ordinary day the first three do most of the work, because the room is cooler than you are.

On a hot day they quit. A room at 95 °F is warmer than your skin, so radiation and convection reverse and start delivering heat to you instead. What is left is evaporation, and it has one requirement: the air has to be willing to accept water.

That is what relative humidity measures. Air already carrying most of the water it can hold takes very little more, so sweat sits on skin instead of leaving it, and sitting sweat cools nothing. You are wet, miserable, and still warming up.

Understand that one mechanism and everything below stops being a list. What helps water leave skin helps. What only feels nice does not.

Why the porch thermometer is not the number that matters

The heat index is the National Weather Service’s answer to exactly this. It defines it as a measure of how hot it really feels when relative humidity is factored in with the actual air temperature.

Two things about that number matter before you use it. It was devised for shady, light wind conditions — and the NWS says exposure to full sunshine can increase heat index values by up to 15 °F. And the categories underneath are not decoration: the NWS chart sorts readings into Caution from 80 to 90 °F, Extreme Caution from 90 to 103, Danger from 103 to 124, and Extreme Danger at 125 and above, where heat stroke is described as highly likely.

The grid below is that chart, drawn out. Move the humidity slider without touching the temperature and watch your cell walk sideways into another band.

Heat index grid — the NWS chart, with a crosshair

What the air is actually doing to you, once the humidity is in the number

Move the two sliders and watch the cell travel. Then pin it and move only the humidity: that second number is the one nobody's thermometer shows.

Air temperature — 92 °F Relative humidity — 45 %

Standing in full sunshine

—

Heat index in °F — air temperature down the side, relative humidity across the top
°F \ RH	40	45	50	55	60	65	70	75	80	85	90	95	100
80
82
84
86
88
90
92
94
96
98
100
102
104
106
108
110

The notebook — running the NWS equation at one temperature

I took the Rothfusz regression that NOAA’s Weather Prediction Center publishes and ran it at a single air temperature, 92 °F, changing only the humidity. At 45 percent it returns 96 °F, which is Extreme Caution on the NWS scale. At 80 percent it returns 121 °F, which is Danger. Twenty-five degrees of apparent heat from water vapor alone, on a day where every thermometer on the street agrees it is 92 out. Add the sunshine clause — up to 15 °F for standing in the open rather than in the shade the chart assumes — and the humid version of that afternoon runs off the end of the chart. Which is the case for owning a hygrometer rather than a thermometer: the forecast high is the shaded, ventilated, best-case version of the day.

Cool the person before you try to cool the house

Here the usual advice inverts. The house is a slow, expensive, low-yield target. The person is fast, cheap, and cooled in about four minutes.

Water on skin, then air over it. A cool shower is the most effective thing in an ordinary home, which is why the CDC lists cool showers or baths among the ways to stay cool without air conditioning. Short and repeated beats long and once. When a shower is not practical — a small child, limited mobility, an outage with no water pressure — a wet cloth on the neck, the inner forearms and the ankles does a smaller version of the same job. Evaporative cooling towels^aff. are the purpose-built version, working on exactly this principle, which is also why they stop working the moment the air is saturated. Wring them out. Do not let one go warm and stay on.

Wear less, and looser. Cotton or linen, loose enough that air moves between fabric and skin. Tight synthetics trap a saturated layer against the body: the humid-air problem in miniature.

The fan, and the hour it stops helping

A fan does not cool air. It moves it. Everything it does for you it does by speeding evaporation off your skin and stripping away the thin layer of warm air against you.

So it is excellent right up to the point where one of two things becomes true. If the air is hotter than your skin, moving more of it over you delivers heat rather than removing it. And if the air is so humid that sweat is not evaporating anyway, the fan has nothing left to accelerate.

This is not a subtlety invented here. Ready.gov’s wording is that fans create air flow and a false sense of comfort, but do not reduce body temperature or prevent heat-related illnesses. The CDC says not to rely solely on fans, because when temperatures are really hot they will not prevent heat-related illness.

At home: use the fan on damp skin, not dry skin, and to move air out of the house at night rather than to stir a shut room at three in the afternoon. Never let a fan be the reason somebody decides they can skip the cooled building.

A 20-inch box fan^aff. set backwards in a window, blowing outward, beats three fans pointed at people: it pulls the whole house through whatever is open on the other side. That is the tool for the night. The small fan on the table is the tool for the body.

Drinking, on a schedule

Thirst arrives late. By the time you notice it you are behind, and in heat the deficit compounds over days rather than hours.

What works is a bottle within arm’s reach, refilled at fixed times rather than when you remember. An insulated 32-ounce bottle^aff. holds a quarter of a day’s planning figure and keeps it drinkable in a room at 90 °F, which a plastic bottle on a windowsill does not.

Ready.gov’s instruction is to drink plenty of fluids to stay hydrated. The household figure behind it — one gallon per person per day — is the one in emergency water storage, and heat is where a gallon is a floor rather than a target. Skip alcohol during the hot hours. Use the stove and oven less, which is the CDC’s own suggestion for keeping a home cooler, and eat things that need no cooking.

The house: shut it by day, flush it at night

Now the building, in second place where it belongs.

An unconditioned home has one free cooling mechanism and it runs overnight: push out the air the house has been heating all day, pull in cooler air from outside. Everything else is damage control on the load coming in.

So the two decisions that matter are hours on a clock. The hour you shut the house, and the hour you open it. Get those backwards — windows flung open at two in the afternoon because the room feels stuffy — and you spend the evening sleeping in heat you invited in. A smoky summer removes the option entirely: with wildfire smoke outside, the house stays shut and the air gets filtered instead, which is the clean room in wildfire home protection.

Stuffy and hot are different complaints. Only one of them is dangerous.

Sun through glass is where most of the load arrives, so that is where it gets stopped, preferably before it is inside: an awning, an exterior shade or a shutter beats anything hanging indoors. Failing that, blackout thermal curtains^aff. on the west-facing windows, closed by mid-morning and left closed, are the highest-return thing most renters can do. Hang them in May. Nobody does it in July, because in July everyone is too hot to stand on a chair.

The dial below is the schedule, not the weather. Set your own hours and it counts the heat you are letting in and the free cooling you are sleeping through.

Night flush dial — twenty-four hours, two markers

When your house is open, and whether that is when the air is worth having

Set the hours you actually close and open the house, then say when the outside air passes the inside on a bad day where you live. The ring does the rest. Nothing here is a temperature forecast — it is your own schedule, counted.

Open while the outside air is hotter
Open while it is cooler — the flush
Shut while it is hotter — holding
Shut while it is cooler — wasted

I shut the windows and blinds at I open them again at Outside passes the inside around It drops back below around Overnight, the air outside gets down to

0 h of outside heat let in

0 h of free cooling missed

One room, not the whole home

The instinct to keep the whole home livable is what exhausts households on day three. Pick one room and give up on the rest.

The candidate is usually the lowest floor, shaded side, fewest windows, door that closes. A north-facing ground-floor bedroom beats a bright open-plan living room, and a basement beats both. Shut it in the morning, put the people and the cooling effort there, and let the kitchen sit at 88 °F because nobody is in it.

Top-floor apartments are the hard case: the roof radiates into the ceiling all night, so the flush works worse there than anywhere else. In that building the room matters less than the hours you spend somewhere with air conditioning.

Reading the alerts, and finding the building with air conditioning

Heat comes with warning, which distinguishes it from almost everything else in natural disaster preparedness. The forecast is usually right days ahead — if you know what the words mean.

The National Weather Service issues an Extreme Heat Warning when extremely dangerous heat conditions are expected or occurring, an Extreme Heat Watch when conditions are favorable for an extreme heat event but its occurrence and timing is still uncertain, and a Heat Advisory for dangerous heat conditions that are not expected to reach warning criteria.

The part people miss is that none of those thresholds is national. Local offices set them with local partners, and the agency gives its own example: residents of Florida are much more prepared for 90 °F weather than residents in Alaska.

The alert	What it means	What it changes at home
Heat Advisory	Dangerous heat, below warning criteria	Move outdoor work to early morning. Call the people on your list.
Extreme Heat Watch	Conditions favorable, timing uncertain	Buy now, hang the curtains, check the cooling center’s hours.
Extreme Heat Warning	Extremely dangerous heat expected or occurring	Nobody at risk rides it out at home.

Receiving the alert matters more in heat than people assume, because heat waves and outages arrive together and a dead phone receives nothing. A receiver on its own transmitters is the fix, and the criterion that decides it is county-level SAME coding, without which the thing gets unplugged in a week for announcing the next county’s storms — a NOAA weather radio with SAME programming^aff. is the version that survives a season. Which one suits which household is worked through in the emergency weather radio guide.

Then the most effective move available without air conditioning: go somewhere that has it. Your county or city health department opens and lists cooling centers, many areas answer on the 2-1-1 line, and the CDC points at the ordinary fallbacks — shopping malls, public libraries — noting that even a few hours spent in air conditioning can help.

Find the address in April. Write it on paper. A cooling center you have to search for on a dying phone at four in the afternoon is one you will talk yourself out of.

A heat wave without AC when the power is out too

This is the real version for most American households, and the one where the timeline gets short.

The outage takes the air conditioning, the fans, the elevator and, in a building tall enough to need a booster pump, the water in the upper-floor taps. On the Gulf and Atlantic coasts the outage long enough to matter usually arrives attached to a storm, which is the week hurricane preparedness is written for. The house keeps absorbing heat and loses its only way of shedding it. Meanwhile the refrigerator has about four hours and a full freezer about forty-eight, which the extended power outage article works through hour by hour.

Fill containers in the first ten minutes, not the first hour — which only happens if the containers are already in the house, so the criterion is storage rather than capacity and collapsible water containers^aff. that fold flat in a closet beat rigid drums nobody has room for. Keep the appliance doors shut. Move everyone to the chosen room and start the flush the moment the outside air is worth having.

What a battery runs, and what it does not

This is where money gets wasted, so be exact.

A portable power station runs fans, phones, a lamp, a radio and a CPAP, quietly and without exhaust, which makes it the sane choice in an apartment. What it does not run is air conditioning. Cooling is thousands of watts sustained for hours, and a battery sized for a household kit empties against a window unit in well under an hour. Anyone saying otherwise is quoting a spec sheet with no runtime attached.

A small rechargeable clip-on fan^aff. is the honest version of backup cooling: many hours off a power bank, pointed at one person, and the difference between sleeping and not. For the larger capacity, a portable power station^aff. covers fans, phones and a radio for a couple of days, and the case against a generator is argued criterion by criterion in portable power station versus generator.

Generators stay outdoors, at least twenty feet from windows, doors and attached garages. That rule is broken more often in heat than in winter, because people want the machine close enough to run a cord through a window, and that is exactly the geometry that kills. The reasoning behind three days of self-sufficiency sits in why 72 hours, and the quantities in the 72-hour kit checklist.

Who is at risk, and the knock on the door

Heat does its damage quietly, indoors, disproportionately to people who are alone. That fact reorganizes everything above.

The CDC names the groups: people 65 years of age or older, infants and young children, and those working or exercising outside in the heat. It adds the line that catches households by surprise — many medicines can make you dehydrated or overheated on hot days. Ready.gov’s list runs the same way, including people with chronic medical conditions, and the NWS adds pregnant women.

So preparing for heat includes something no other hazard here asks for: a list of names. Two or three people — the neighbor upstairs who is 80, the friend who lives alone, the relative on the medication — that you call or visit during the warning rather than after. Agree on it in spring, when it still sounds fussy.

And the rule that never stops being necessary: nobody is left in a parked car. Not for five minutes, not with the windows cracked. The NWS reports that 31 children died in hot cars in 2025, and that such deaths are reported as early as April and continue into December in southern states.

Heat illness is a 911 call, not a home remedy

Nothing on this page treats a symptom, and nothing on it should ever be used as though it did. Ready.gov describes heat stroke as an extremely high body temperature — above 103 °F — with red, hot and dry skin and no sweat. That, along with confusion, slurred speech, staggering, fainting, or a person who has stopped making sense in the heat, is an emergency: call 911 immediately, say the person has been in the heat, and do what the dispatcher tells you while help is coming. Do not wait to see whether a cool shower, a wet towel or a glass of water helps first — those are comfort measures for a well person, never a treatment, and the minutes spent trying them are the ones that matter. Anyone taking medication for blood pressure, the heart, a psychiatric condition or anything with a diuretic effect should ask their own physician or pharmacist what heat does to it, before the season. Anyone dependent on a powered medical device belongs on their utility’s medical priority list, with a written plan for where they go when the power fails.

What does not help, including the things that sell well

The portable “air cooler” that is really an evaporative unit. In a dry climate it genuinely works. In a humid one it adds water to air that already had too much — the precise opposite of what your skin needs — with a fan’s false comfort attached.

The bowl of ice in front of a fan. It does something for about eleven minutes, then it is a bowl of water and a fan, and in a closed room the water it added is working against you.

And the one that sounds prudent and is not: toughing it out at home because a cooling center feels like something for other people. If a household member is on the CDC’s list, a few hours in air conditioning is the intervention, and everything else here is what you do around it.

The dull purchases earn their place instead: a hygrometer, curtains hung in spring, one good fan, a full water reserve. All of it belongs on the equipment page, and none of it costs what a failed compressor does.

The week to do this in is not this one

If you are reading this during a heat wave, do the short list: shower, damp cloth, one room, flush after dark, water on a schedule, and the nearest air-conditioned building for the afternoon.

If you are reading it in October, you have the better opportunity. Curtains go up in a cool month, the hygrometer finds your own crossover hour over a few ordinary days, and the fan gets bought before the shelves are empty.

Heat is the hazard with the longest warning and the worst record, which only makes sense once you see what preparing for it costs: an hour, in a month when nobody feels like thinking about it. The rest of the preparedness articles run the same way, and the tiers beyond three days are in long-term emergency preparedness. If you want to know who writes this and why, that is here.

Frequently asked questions

How do you get through a heat wave without AC?: You cool the person, then the house, and in that order. The body sheds heat by evaporating sweat, so the useful moves are the ones that help water leave skin: a cool shower, a wet towel on the neck and forearms, loose clothing, and moving air across damp skin rather than dry skin. Then the building: shut it up before the outside air passes the inside temperature, blinds down on the sunny side, and open everything once the outside air has dropped back below. Pick one room and defend it instead of the whole home. And know where the nearest air-conditioned public building is, because a few hours there does more than anything you own.
Do fans actually help in extreme heat?: They help until the air gets hot enough that they stop, and the switchover is invisible. A fan does not cool air, it moves it, and what it buys you is faster evaporation from skin. Once the air is hotter than your skin, moving more of it over you adds heat rather than removing it, and if the humidity is high enough that sweat is not evaporating, the fan has nothing left to work with. Ready.gov puts it bluntly: fans create air flow and a false sense of comfort, but do not reduce body temperature or prevent heat-related illnesses. The CDC's version is the same — do not rely solely on fans to keep you cool.
What is the heat index and why is it higher than the temperature?: The heat index is how hot it feels once relative humidity is combined with the air temperature, and it is higher because humid air makes your own cooling system work worse. Sweat only cools you when it evaporates, and it evaporates slowly into air that is already carrying water. The number moves a long way: 92 °F at 45 percent humidity reads 96 °F on the National Weather Service chart, and the same 92 °F at 80 percent humidity reads 121 °F. The chart is also built for shade and light wind, and the NWS says full sunshine can add up to 15 °F on top.
What is the difference between an extreme heat warning and a heat advisory?: The National Weather Service issues an Extreme Heat Warning when extremely dangerous heat conditions are expected or occurring, an Extreme Heat Watch when conditions are favorable for an extreme heat event but its occurrence and timing are still uncertain, and a Heat Advisory for dangerous heat conditions that are not expected to reach warning criteria. The thresholds are not national. Local offices set them with local partners, and the NWS says so plainly using its own example: residents of Florida are much more prepared for 90 °F weather than residents of Alaska. Your advisory and somebody else's warning can be the same forecast.
Where do I find a cooling center?: Start with your county or city health department, which is the body that opens them and publishes the list, and with your local emergency management page. Many areas also answer this on the 2-1-1 line. If nothing is open yet, the CDC points at the ordinary substitutes: shopping malls and public libraries, noting that even a few hours spent in air conditioning can help. Ready.gov says the same thing about finding an air-conditioned place to be. Sort this out on a mild week and write the address somewhere that is not your phone, because looking it up for the first time on the worst afternoon of the year, on a dying battery, is how people decide to stay home instead.
How much water should you drink during a heat wave?: More than thirst asks for, and steadily rather than in one go, because thirst lags behind what the body has already lost. The practical version is a bottle within reach that you refill on a schedule, and drinking on the clock rather than when you notice. Keep the household's stored water topped up too: the standard planning figure is one gallon per person per day, and heat is exactly the situation where that figure is a floor. Anyone on a fluid restriction, a diuretic, or medication for blood pressure or the heart has a different answer, and the person who gives it is their doctor or pharmacist, not a website.
What do I do if the power goes out during a heat wave?: Treat it as a clock, not an inconvenience. Without power the house keeps absorbing heat and stops being able to shed any, the fans stop, and in a tall building the water can stop as well. Fill containers early, keep the refrigerator and freezer shut, and move to the coolest room. Then make the call most households postpone too long: if anyone in the house is over 65, under two, pregnant, on a daily medication that affects heat tolerance, or dependent on a powered medical device, they leave for an air-conditioned place rather than waiting for the grid. A battery will run fans, phones and a radio. It will not run air conditioning.
What are the signs of heat stroke?: Ready.gov describes an extremely high body temperature, above 103 °F, along with red, hot and dry skin with no sweat, and that combination is a 911 call made immediately, not a reason to try something at home first. Confusion, slurred speech, staggering, fainting or a person who has stopped making sense are the same emergency. Nothing on this page treats any of that — no wet towel, no cool shower, no glass of water is a treatment, and improvising one costs the minutes that matter. Call 911, say the person has been in the heat, and follow the instructions the dispatcher gives you while help is on the way.

Who wrote this

Baptiste S.

Founder and writer · bs-media

I am not a firefighter, a paramedic or a survival instructor. I am someone who read his government's household preparedness guide cover to cover, lives where winter storms knock the power out every year, and decided to do the work properly: read the official guidance, run the numbers, compare the spec sheets, and write down what I wish I had found. This site sells neither fear nor bunkers. It explains what an ordinary household can put together in a weekend, and in what order.

I start from official guidance — FEMA, Ready.gov, the National Weather Service, the CDC, the American Red Cross — and I link to it. If I have not checked it, I do not write it.
No guns, no bunkers, no doomsday: this site prepares an ordinary household for three days, two weeks, a month.
I say what is not worth buying, including the things that sell best in survival stores.
On health, medication and electrical work, I defer to your doctor, your pharmacist or a licensed electrician. That is not my job.