Extreme Heat Safety: How to Stay Cool During a Heat Wave and Outage

Quick answer: plan where you will go to cool off before the heat arrives, drink water steadily, keep out of the sun during the hottest hours, and check on older neighbors and anyone living alone. Learn the warning signs of heat exhaustion and heat stroke. Heat stroke is a medical emergency, so call 911. If the power goes out, move to an air-conditioned public place rather than relying on a fan in a hot apartment.

A heat wave does not look like a disaster. There is no wind damage, no flood line on the wall, nothing on the news footage but people squinting into the sun. That is part of what makes it dangerous. The CDC describes extreme heat as one of the leading weather-related causes of death in the United States, and many of those deaths happen quietly, indoors, to people who did not have a cool place to go.

City living adds its own twist. Pavement, brick and concrete soak up heat all day and release it at night, so urban neighborhoods often stay warmer after sunset than nearby suburbs or countryside. The EPA calls this the urban heat island effect. Upper floors of older buildings can turn into ovens, and a power outage during a heat wave removes the one tool most households lean on.

This guide covers how to prepare, how to keep your space cooler, what heat illness looks like, and what to do if the air conditioning stops. Nothing here replaces a doctor or emergency services. Treat it as a planning checklist, not medical advice.

Understand Heat Alerts and Who Is Most at Risk

The National Weather Service issues heat products based on local conditions, because what counts as dangerous in Phoenix differs from what counts as dangerous in Seattle. In 2025 the agency renamed its Excessive Heat Watch and Warning to Extreme Heat Watch and Extreme Heat Warning. A watch means dangerous heat is possible in the coming days. A warning means it is expected or already happening, and a Heat Advisory signals conditions that are less severe but still risky for many people.

Pay attention to the heat index, not just the thermometer. The heat index combines air temperature and humidity to estimate how hot it actually feels. Humid air slows the evaporation of sweat, and sweat evaporating off your skin is the main way your body sheds heat. A 92-degree day with heavy humidity can be harder on the body than a drier day several degrees hotter.

Certain people face higher risk, according to the CDC:

• Adults 65 and older, whose bodies adjust to temperature changes less efficiently
• Infants and young children, who depend on adults to keep them cool and hydrated
• People with chronic conditions such as heart disease, high blood pressure or diabetes
• Anyone taking medications that affect hydration or temperature regulation, so ask a pharmacist about yours
• Outdoor workers and athletes
• People who live alone, have limited mobility, or lack air conditioning

Make a short list of the people in your life who fit those groups. During a heat event, a phone call or a knock on the door twice a day is one of the most useful things a neighbor can do. Add it to your family emergency communication plan so everyone knows who checks on whom.

Prepare Before the Heat Wave Arrives

The best time to plan for heat is on an ordinary spring afternoon. A few steps now save a lot of scrambling later.

Find your cool places

Many cities and counties open cooling centers during heat emergencies, usually in libraries, community centers or senior centers. Look up how your local government announces them, whether through a website, a 311 line or a text alert service. Note a few backup options too: a public library, a shopping mall, a movie theater, or a friend or relative with reliable air conditioning. Write down hours and how you would get there without driving if needed.

Check your cooling equipment

Clean or replace air conditioner filters before the season. Window units should be installed securely and sealed so cool air does not leak out. Test them on the first warm day rather than the first dangerous one, since repair technicians get booked quickly once a heat wave hits.

Block heat from coming in

Ready.gov suggests covering windows with drapes or shades and using window reflectors on windows that face the sun. Weather-stripping around doors and windows keeps cool air in. Inexpensive blackout curtains on south and west windows can make a noticeable difference in a small apartment.

Sign up for alerts and keep a kit

Turn on Wireless Emergency Alerts on your phone and sign up for your local alert system. Your basic apartment emergency kit already covers water, a flashlight and a battery radio. For heat, add a few items: extra water, oral rehydration packets, a battery-powered or rechargeable fan, a spray bottle, cooling towels and a fully charged power bank for your phone.

Keep Your Body Cool and Hydrated

Hydration advice sounds obvious until you are busy, distracted, or simply not thirsty. The CDC recommends drinking fluids regularly during hot weather rather than waiting until you feel thirsty. Anyone whose doctor limits fluid intake, or who takes water pills, should ask that doctor how much to drink during a heat wave instead of guessing.

Drinks heavy in sugar and alcohol work against you, and the CDC advises avoiding them in extreme heat. Plain water is the default. During long, sweaty outdoor work, a sports drink can help replace salt and minerals lost through sweat, but people on low-salt diets should check with a doctor first.

Clothing matters more than people expect. Lightweight, loose, light-colored clothing reflects sunlight and lets sweat evaporate. A wide-brimmed hat and sunscreen help, since sunburn reduces the body’s ability to cool itself. Schedule outdoor errands and exercise for early morning or evening, and rest often in the shade if you must be out at midday.

Cool showers or baths bring body temperature down quickly. So does a wet cloth on the neck, wrists and armpits. Eating lighter meals and skipping the oven also helps, because cooking adds heat to your home and digestion of large meals adds a little to your body.

Never leave a child, an older adult, or a pet in a parked car, even with the windows cracked. The CDC warns that the temperature inside a closed car can climb quickly to deadly levels. Make a habit of checking the back seat every time you get out.

Recognize Heat Exhaustion and Heat Stroke

Heat illness tends to build in stages. Catching the early ones gives you time to act. The CDC lists these warning signs.

Heat exhaustion

• Heavy sweating
• Cold, pale and clammy skin
• A fast, weak pulse
• Nausea or vomiting
• Muscle cramps
• Tiredness or weakness
• Dizziness, headache, or fainting

The response: move to a cooler place, loosen clothing, put cool wet cloths on the body or take a cool bath, and sip water. Get medical help right away if the person is vomiting, symptoms get worse, or symptoms last longer than an hour.

Heat stroke

• A high body temperature of 103 degrees Fahrenheit or higher
• Hot, red, dry or damp skin
• A fast, strong pulse
• Headache, dizziness or nausea
• Confusion
• Losing consciousness

This is a medical emergency. Call 911 right away. While you wait, move the person to a cooler place and lower their body temperature with cool cloths or a cool bath. The CDC specifically says not to give a person with heat stroke anything to drink.

Milder problems include heat cramps, heat rash and sunburn, which are still signals that the body is struggling. Muscle spasms during activity in the heat are a reason to stop, rest somewhere cool, and drink water or a sports drink. Anyone with heart problems, or whose cramps last more than an hour, should seek medical help.

When the Power Fails During a Heat Wave

Hot spells strain the electric grid, and outages often arrive right when cooling matters most. Ready.gov and the CDC both stress that if your home becomes dangerously hot, the safest move is usually to leave it. Go to a cooling center, a public building, or a friend’s place with power.

Fans deserve a special note. A fan moves air, which helps sweat evaporate, but it does not lower the air temperature. The CDC cautions that electric fans may provide comfort, yet when temperatures are in the high 90s they will not prevent heat-related illness. Running a fan in a sealed, sweltering room is not a safe plan for an older adult or someone with health conditions.

For people staying put during a shorter outage, these steps help:

• Stay on the lowest floor you can reach, since heat rises and upper floors get hottest
• Keep shades and curtains closed on the sunny side of the building
• Open windows at night only if the outside air is cooler and it is safe to do so
• Take cool showers if water is running, and keep damp towels handy
• Wear as little as is comfortable and keep activity light
• Keep refrigerator and freezer doors closed to protect food

Food safety goes hand in hand with heat. According to FoodSafety.gov, a closed refrigerator keeps food safe for about four hours without power, and a full freezer holds its temperature for about 48 hours, or about 24 if half full. Throw out perishable food that has been above 40 degrees Fahrenheit for two hours or more. Our guide to preparing for a power outage in a high-rise covers elevators, stairwells and water pressure in tall buildings.

If you use a portable generator, follow CDC carbon monoxide rules: run it outdoors only, at least 20 feet from doors, windows and vents, and never in a garage, basement or balcony enclosure. Carbon monoxide has no smell or color, and a battery-operated CO alarm should be in every home that uses fuel-burning equipment.

Look Out for Neighbors and Pets

The people at greatest risk during heat waves are often the least likely to ask for help. A neighbor who has not been seen in a day, mail piling up, or windows closed tight on a sweltering afternoon are all reasons to knock. Building managers and tenant groups can set up a simple sign-up sheet so residents who live alone get a daily check-in during heat alerts. Our article on sheltering in place has more on organizing that kind of building-level plan.

Pets feel heat too. The American Veterinary Medical Association advises giving pets plenty of fresh water and shade, limiting exercise on hot days, and remembering that hot pavement can burn paw pads. Dogs with short snouts, older animals, and pets with heavy coats are especially vulnerable. Heavy panting, drooling, weakness or collapse in a pet means it needs to cool down and see a vet promptly.

Build a Simple Heat Plan You Will Actually Use

A plan only helps if it is short enough to remember. Here is a version you can copy onto an index card and tape inside a kitchen cabinet:

1. Where we go to cool off: name of cooling center or friend’s home, plus a backup
2. How we get there without a car
3. Who we check on, and how often
4. Medications that are affected by heat or need refrigeration
5. Signs of heat stroke: high temperature, confusion, hot skin, so call 911
6. Our outage steps: lowest floor, shades down, fridge closed, leave if it gets dangerous

Review the card once each spring. Swap out expired water, test fans and power banks, and confirm the cooling center list for the coming summer. That small routine turns a scary forecast into a list of things you already know how to do.

Frequently Asked Questions

What temperature is dangerous for a heat wave?

There is no single number. Danger depends on humidity, how used to heat your area is, and personal health. That is why the National Weather Service sets heat alert thresholds locally. Pay attention to the heat index and to any Extreme Heat Warning or Heat Advisory in your area.

Can a fan keep me safe in extreme heat?

Not on its own once temperatures are very high. The CDC says fans may provide comfort but will not prevent heat-related illness when it is in the high 90s. Use a fan alongside cool showers and a cooler location, and leave the building if it becomes dangerously hot.

How can I tell heat exhaustion from heat stroke?

Heat exhaustion usually brings heavy sweating with cool, clammy skin, plus dizziness, nausea or cramps. Heat stroke involves a body temperature of 103 degrees or higher, hot red skin that may be dry or damp, confusion, or passing out. Heat stroke needs 911 right away.

Should I drink sports drinks during a heat wave?

Water is the main choice. A sports drink can help replace salt and minerals during long, heavy sweating. People on low-salt diets or with medical conditions should ask a doctor first.

What should I do if my apartment has no air conditioning?

Know where your nearest cooling center or air-conditioned public space is and go during the hottest part of the day. At home, block the sun, stay on a lower floor if you can, take cool showers, and check in with someone daily.