What to Do When the Power Goes Out During a Heat Wave

A power outage is an inconvenience most of the year. During a heat wave, it is a genuine emergency. The air conditioning that keeps your home livable shuts off at the exact moment you need it most, indoor temperatures start climbing within the hour, and the refrigerator full of food begins a quiet countdown. For older adults, infants, and anyone managing a chronic condition, a hot house without power can turn dangerous fast.

The frustrating part is that heat and outages are not a coincidence — they cause each other. The same scorching afternoons that send everyone's air conditioner into overdrive are the afternoons that push the electric grid to its limits. That is why the playbook below matters: not just what to do in the first ten minutes, but how to stay cool, keep food and medicine safe, run backup power without poisoning yourself, and set up your household so the next outage is a nuisance instead of a crisis.

Why Heat-Wave Outages Are Uniquely Dangerous

Most blackouts are random — a storm, a car into a pole. Heat-wave blackouts are different: they are predictable, and they strike when the stakes are highest. On very hot days, air-conditioning demand pushes grid stress to its peak during roughly 3 to 8 p.m., and that late-afternoon window is exactly when outages and rolling blackouts are most likely. We covered this dynamic in detail in our report on the heat wave blackout danger window, and the pattern holds across most of the country.

Think about what that timing means. The outage does not hit at 4 a.m. when the house is at its coolest. It hits when outdoor temperatures are near their daily high, your home has been absorbing heat all day, and the sun still has hours left to work. A house that traps heat may stay hotter than the outdoors well into the night.

The second danger is duration uncertainty. A rolling blackout may end within the hour; a heat-driven equipment failure can stretch into days. Since you rarely know which you are facing, act as if the outage will be long — starting with the clock on your refrigerator.

The First Ten Minutes: Immediate Steps

When the lights go out on a hot day, do these things before anything else:

1. Note the time. Write it down or say it into your phone. The moment power fails, the food-safety clock starts, and knowing exactly when it started will tell you later what is safe to eat.
2. Keep the refrigerator and freezer doors closed. Every time you open a door, cold air spills out and your safe window shrinks. Decide now that nobody opens them until power returns or you have a plan.
3. Check whether it is just you. Look at neighbors' homes and check your utility's outage map on your phone. A whole-neighborhood outage during peak heat likely means grid strain, and it may be a rolling blackout that ends soon.
4. Report the outage. Utilities prioritize by reports. Do not assume someone else has called it in.
5. Shed the heat you can control. Turn off and unplug anything that generates heat or could surge when power returns — ovens, stovetops, computers. Close blinds and curtains on sun-facing windows.

Then take a breath. Most outages are short; the rest of this guide is for when minutes turn into hours.

How to Stay Cool Without Power

Your body can handle a warm house for a while if you manage heat deliberately. The goal is to slow how fast your home warms up and to keep your core temperature down.

Move low. Heat rises, so the lowest floor of your home — a basement if you have one — will be the coolest place. Set up there with water, a battery-powered or manual fan, and anything else you will want, so you are not making trips upstairs.

Manage windows by the thermometer, not by habit. Opening windows only helps when it is cooler outside than inside — typically at night and in the early morning. During the afternoon, open windows just let hot air in. Keep the house sealed and shaded through the hottest hours, then open windows on opposite sides of the house after dark to pull a cross-breeze through.

Cool your body directly. Damp cloths on pulse points — the neck, wrists, and ankles — cool the blood near the skin's surface and lower how hot you feel. Cool showers work even better, and here is a piece of good news: municipal water systems usually keep flowing during a power outage, so the shower is one appliance you have not lost. Drink water regularly, even before you feel thirsty; sweating without replacing fluids is how heat illness starts.

Use small power wisely. A battery-powered fan pointed at damp skin does far more than the same fan across the room. For a deeper set of techniques — evaporative cooling, timing your day around the heat, and low-tech tricks that predate air conditioning — see our companion guide to staying cool without AC.

When to Stop Toughing It Out and Go to a Cooling Center

There is a point where home cooling tricks are not enough, and recognizing it early matters more than any other decision in this guide. If you cannot get your body to cool down despite everything above — the shaded rooms, the damp cloths, the cool showers — it is time to leave. And for older adults, infants, and people with chronic conditions, the bar should be much lower: do not wait until someone is clearly unwell.

Cooling centers are air-conditioned public spaces — libraries, community centers, dedicated shelters — that cities open during dangerous heat. They are free, and you do not need to be in visible distress to use one. In most areas you can dial 211 to find the nearest location, or use our cooling center finder to look up what is open near you. If you live in a major metro, we maintain dedicated pages for cities including Phoenix and Houston, where summer outages carry the highest stakes.

One counterintuitive tip: go during the hottest hours, not after you have suffered through them. The afternoon peak is when your home is most dangerous and the cooling center is most valuable. Treat it like riding out a storm somewhere safe — you can come home when the danger window passes or the power returns.

Food and Medication Safety

The 4-24-48 Rule for Food

A closed refrigerator or freezer is better insulated than most people think, but the safe windows are finite. The numbers below assume you keep the doors shut.

Appliance	Condition	Food stays safe for about
Refrigerator	Unopened	4 hours
Freezer	Full, unopened	48 hours
Freezer	Half full, unopened	24 hours

A full freezer lasts twice as long as a half-full one because frozen food acts as its own thermal mass — which is why some people keep jugs of frozen water in the empty space year-round. If an outage is running long, move refrigerated essentials into the freezer or an insulated cooler with ice, in one quick, planned opening.

When power returns, an appliance thermometer removes the guesswork: if the refrigerator held at or below 40°F, the food inside is fine. Without a thermometer, you are judging by time and smell — and smell is unreliable, because the bacteria that cause foodborne illness often produce no odor at all. The rule that settles every argument: when in doubt, throw it out. No leftover is worth food poisoning during a heat wave.

Keeping Medications Cold

Insulin and other refrigerated medications need a plan within the first few hours. Move them to an insulated cooler with ice packs — but not resting directly on ice, because freezing can ruin insulin just as surely as heat can. Wrap the medication in a towel or keep it in a container that separates it from the ice packs.

Then call a pharmacist. Many refrigerated medications tolerate room temperature for a surprising stretch, and your pharmacist can tell you exactly how long yours keeps outside refrigeration and what signs of spoilage to look for. Make that call early, while your phone still has charge, rather than guessing later.

Backup Power Without the Backup Tragedy

Small-scale power is easy and safe. A portable power station — essentially a big rechargeable battery — can run phones, a small fan, and a lamp for hours with zero risk. Your car's USB ports will top off a phone too; just never idle a car in a closed garage, where exhaust builds fast. Best habit of all: charge everything — phones, battery banks, rechargeable fans — the day before forecast extreme heat. Heat-wave outages are among the few emergencies that announce themselves in advance.

Generators are where outages turn deadly, and it is almost never the electricity — it is the exhaust. Carbon monoxide is invisible, odorless, and kills quickly. Every summer, people die running generators in garages, on covered porches, or just outside an open window. The rules are absolute:

• Never run a generator indoors. Not in the house, not in the garage, not in the basement — not even with doors and windows open.
• Keep it at least 20 feet from windows, doors, and vents, with the exhaust pointed away from the house. Closer than that, carbon monoxide can drift inside and accumulate.
• Install battery-powered carbon monoxide alarms if you own a generator. In an outage, plug-in alarms without battery backup are dead too.

The same logic applies to cooking: never burn charcoal or run a gas camp stove indoors. Grill outside, well away from windows, or eat the shelf-stable food in your kit.

Checking on the People Who Cannot Ride It Out

Heat deaths during outages are concentrated among people who live alone and could not — or would not — ask for help. If you have elderly neighbors, check on them at least twice a day during an outage. Knock, talk to them, make sure they are drinking water and able to cool down, and take note of a home that feels like an oven. Offer a ride to a cooling center; many will not ask until someone makes it easy to say yes.

Children and pets need the opposite kind of vigilance. Never leave a child or a pet in a parked car, not even for a few minutes with the windows cracked — cars heat to lethal temperatures with astonishing speed. During an outage, keep pets on the lowest, coolest floor with you and make sure they have plenty of water.

Preparing for the Next One

Heat-wave outages will keep happening, and the households that handle them well are the ones that prepared on a cool day. Your checklist:

• An emergency kit with drinking water and shelf-stable food that needs no cooking.
• A charged battery bank (or portable power station) and the habit of topping it off whenever extreme heat is in the forecast.
• Flashlights with fresh batteries — not candles, which add heat and fire risk.
• An appliance thermometer in the refrigerator, so post-outage food decisions are facts instead of guesses.
• A battery-powered or manual fan and a stash of ice packs in the freezer, which double as cooler packs for food and medication.
• Your nearest cooling center, identified in advance. Look it up now — Chicago residents can start with our Chicago cooling centers page — and save the address. Deciding where to go is much harder in a sweltering living room than it is today.

The through-line of all of it: heat-wave outages are predictable emergencies. They come in the late afternoon, on the hottest days, with warning in the forecast. A household that charges its batteries, fills its freezer gaps with ice, and knows where the nearest cool building is has already won most of the battle before the lights flicker.

Frequently Asked Questions

How long does food last in the fridge and freezer during an outage?

An unopened refrigerator keeps food safe for about 4 hours. A full freezer holds safe temperatures for about 48 hours, and a half-full freezer for about 24 hours. Those windows assume you keep the doors closed — every opening shortens them. An appliance thermometer removes the guesswork: food in a refrigerator that stayed at or below 40°F is safe. When in doubt, throw it out.

Can I cook indoors with a gas camp stove during a blackout?

No. Camp stoves, charcoal grills, and portable propane burners all produce carbon monoxide, which is odorless, invisible, and can be deadly indoors even with windows open. Cook outdoors only, well away from windows and doors, or rely on the shelf-stable, no-cook food in your emergency kit until power returns.

Should I open the windows when the power is out in a heat wave?

Only when it is cooler outside than inside — usually at night and in the early morning. During the afternoon, open windows let hot air in and make your home warmer. Keep windows closed and blinds drawn through the hottest hours, then open windows on opposite sides of the house after dark for cross-ventilation.

How do I keep insulin cold without a refrigerator?

Move insulin and other refrigerated medications into an insulated cooler with ice packs, but do not place them directly on the ice — freezing can damage insulin. Keep a towel or container between the medication and the packs. Then call a pharmacist and ask how long your specific medication keeps outside refrigeration; many tolerate room temperature longer than people expect.

Where is my nearest cooling center?

In most areas, dialing 211 will connect you with local cooling center locations and hours. You can also use our cooling center finder at water-restrictions.com to look up open locations near you, including dedicated pages for major cities. The best time to find yours is before the outage — save the address now so the decision is easy on a hot afternoon.

When should I leave home instead of trying to stay cool?

Leave if you cannot get your body to cool down despite shaded rooms, fans, damp cloths, and cool showers. Older adults, infants, and people with chronic conditions should go to air conditioning early rather than waiting until someone is clearly unwell. Go during the hottest hours of the day — that is when home is most dangerous and a cooling center helps most.