When the Power Goes Out
When your home becomes the hazard.
Heat kills more Americans each year than any other weather event. When the air conditioning stops during a heat wave, the clock starts. Knowing how to cool a body, cool a room, and decide when to leave is the difference between discomfort and danger.
By Dan Whelan, founder of New World Survival
Researched from government agencies, university extension services, and other published sources. See our sources
Immediate Actions
The first hour without AC
Your home holds its temperature for a while after the power goes out, but the insulation that keeps heat out also traps it once it starts building. These five steps slow the rise and buy you time.
Close blinds and curtains on sun-facing windows
Solar gain through windows is one of the fastest ways a house heats up. Close every blind, curtain, or shade on windows that face the sun. South- and west-facing windows are the highest priority. If you have reflective window film or exterior shade screens, these are even more effective because they block heat before it enters the glass.
Move to the lowest floor and choose one room
Hot air rises. The lowest floor of your home is the coolest. A basement, if you have one, can be 10 to 15 degrees cooler than the upper floors. Choose one small, shaded room on that floor as your designated cool room. Close the doors to every other room and concentrate your household there. Bring water, medications, phone chargers, and anything you need so you do not have to go upstairs. The next section covers how to set up this room for maximum effect.
Reduce internal heat sources
Do not use the oven or stove. Do not run the dishwasher or clothes dryer if you have any remaining power. Every appliance that generates heat makes the house warmer. Eat cold food, sandwiches, fruit, and foods that do not require cooking. Open the refrigerator and freezer as little as possible to preserve cold.
Check outdoor air before opening windows
If the outdoor air is cooler than indoor air (typically early morning and after sunset), open windows on opposite sides of the house to create a cross-breeze. Open windows low on the windward side and high on the leeward side. During the hottest part of the day, keep windows closed with blinds drawn. Bringing in 100-degree air makes things worse, not better. Also check local air quality alerts: during wildfire season or after industrial events, outdoor air may carry smoke or contaminants that make ventilation unsafe.[6]
Start hydrating now
Do not wait until you feel thirsty. Drink water steadily throughout the day. Avoid alcohol and caffeine, both of which accelerate dehydration. If you have electrolyte packets or sports drinks, use them. An adult should drink at least one cup of water every 15 to 20 minutes during sustained heat exposure.[1]
Your Refuge
Set up a designated cool room
Trying to cool an entire powerless home is a losing strategy. The air volume is too large and the heat gain too fast. Instead, concentrate your household in one small room and make that room as cool as possible. This is the single most effective thing you can do during a summer power outage.
Choose the right room
Pick a small room on the lowest floor of your home, ideally a basement room, an interior room, or one with minimal windows. Avoid rooms with south- or west-facing windows. Smaller rooms cool faster and hold cool air longer. A bathroom or interior hallway with no windows can work if it has enough space for your household to rest comfortably.
Block radiant heat
If the room has any windows, cover them completely. Reflective window film is ideal because it blocks heat before it enters the glass. Emergency Mylar blankets taped to the inside of the glass, shiny side out, are nearly as effective and cost very little. Even aluminum foil or heavy cardboard reduces solar gain significantly. The goal is to stop radiant heat from entering through the glass, not just to block light.
Seal the space
Close the door and roll a towel against the gap underneath to slow hot air from entering. Close doors to every unused room in the house. Each closed door reduces the volume of air that the rest of the house heats. You are creating a small, isolated zone and letting the rest of the house absorb the heat load.
Monitor the temperature
Place a thermometer in the cool room, away from direct sun and electronics. Check it every hour and write down the readings. This is not busywork. It gives you objective data for the most important decision you may face: whether to stay or leave. If the room reaches 95 degrees Fahrenheit and you cannot bring it down, it is time to go somewhere with air conditioning.
Without Electricity
Cool the body, not the room
When you cannot cool the house, cool the person. The body loses heat through evaporation (sweat), convection (moving air), conduction (contact with something cooler), and radiation. Use all four. These methods require little or no equipment and work immediately.
Forearm and pulse-point cooling
Fill a basin or bucket with cool water and immerse your hands and forearms for two to three minutes. Blood vessels run close to the surface at the wrists, inner elbows, and behind the knees, so cooling these areas lowers your core temperature faster than cooling other skin. A wet towel or bandana draped over the neck and re-wetted when it warms up is the simplest version of this approach. Focus on pulse points first when water is limited.
Cool water immersion
Fill a bathtub or large basin with cool (not ice-cold) water and soak your feet and lower legs. If water is scarce, a sponge bath with cool water works. Even wetting your hair and letting it air-dry provides evaporative cooling for 20 to 30 minutes. Dampen your clothing before sitting in front of a fan for accelerated evaporative cooling. If your water supply is limited, prioritize drinking water over bathing water.
Clothing and activity
Wear loose, lightweight, light-colored clothing in natural fabrics like cotton, which breathe and wick sweat better than synthetics in still air. Remove unnecessary layers. Minimize physical activity during the hottest hours, typically 10 AM to 4 PM. Rest. Every calorie of exertion generates heat your body must then dissipate. Save physical tasks for early morning or evening.
Pre-frozen water bottles
If you froze water bottles or filled containers before the outage, they serve double duty: they help keep your refrigerator and freezer cold, and once they begin melting, you can hold them against pulse points or wrap them in a cloth as a personal cooling pack. The water is safe to drink once thawed. Keeping several gallon jugs of water in the freezer is one of the simplest and most effective preparations for a summer outage.
When fans become dangerous
The CDC recommends using fans only when indoor temperature is below 90 degrees Fahrenheit. Above 90 degrees, a fan blows air that is hotter than your body across your skin, which can raise your core temperature rather than lower it. The American Lung Association describes this as a "false sense of comfort."[1]
Recent research published in JAMA Network Open found that fans may still help between 90 and 100 degrees Fahrenheit when combined with skin wetting in humid conditions (above 60 percent humidity). However, in hot and dry conditions above 100 degrees, fans consistently worsened heat strain in study participants, including older adults.[7]
The practical rule: Below 90 degrees, fans help. Between 90 and 100 degrees, fans help only if you are also wetting your skin and the air is humid. Above 100 degrees, stop using fans and rely on direct water cooling: wet towels, forearm immersion, cool baths, and misting.
DIY evaporative cooling (low-humidity climates only)
In dry climates where humidity is below 50 percent, you can create makeshift evaporative cooling that meaningfully lowers air temperature. These methods do not work well in humid climates because the air cannot absorb more moisture.
Wet sheet method: Hang a damp cotton sheet in front of an open window. As air passes through the wet fabric, evaporation cools it. This can reduce incoming air temperature by 10 to 15 degrees in dry conditions. Re-wet the sheet as it dries.
Bucket cooler: Place a bowl of ice or a frozen gallon jug in front of a battery-powered fan (a portable power station can run one for hours). The fan blows air across the cold surface, cooling it before it reaches you. This is a short-term measure that works while the ice lasts. It is a better use of battery power than running the fan alone in a hot room.
When humidity defeats evaporation
Evaporative cooling, including sweat, wet towels, and misting, works best in dry air. When humidity is high (above 75 percent), evaporation slows dramatically and these methods become less effective. In high humidity, conductive cooling (contact with cool surfaces, cool water immersion) and convective cooling (moving air, below 90 degrees) become more important. This is why hot and humid conditions are more dangerous than hot and dry conditions at the same temperature: your body's primary cooling system, sweating, stops working.
Managing the Day
The daily rhythm of a hot house
A power outage during a heat wave is not a single event. It is a daily cycle you manage until the power returns or you leave. Understanding the rhythm of heat through a day turns reactive decisions into a schedule.
Flush and seal
This is your coolest window. If outdoor air dropped overnight, open windows on opposite sides of the house for 30 to 60 minutes of aggressive cross-ventilation to flush out trapped heat. Then, before the sun reaches your windows, close and seal everything: windows shut, blinds drawn, towels under doors. You are locking in cool air for the day.
Defend and rest
Stay in the cool room. Keep everything sealed. Minimize activity. Drink water steadily. Use personal cooling methods: wet towels on pulse points, forearm immersion, damp clothing. Do not cook. Do not open the refrigerator or freezer unless necessary. This is the hardest stretch. The temptation is to do things. Resist it. Every calorie of effort becomes heat.
Ventilate
Once the outdoor temperature drops below your indoor temperature, open windows on opposite sides for cross-ventilation. Check the thermometer: if outdoor air is still hotter than indoor air, wait. When the crossover happens, open aggressively. This is also the time for any physical tasks, cooking (outdoors if possible), and movement.
Sleep strategy
Sleep on the lowest floor. Use cotton sheets only, and dampen them with cool water before lying down. Keep a basin of cool water and a cloth beside the bed. If the room is below 90 degrees, a battery-powered fan aimed at your body helps. If you have a camping hammock, using it instead of a mattress allows air to circulate beneath you, which can feel five to ten degrees cooler than a foam or spring mattress that traps body heat. Keep windows open for cross-ventilation as long as outdoor air is cooler.
Recognize the Danger
Heat exhaustion vs. heat stroke
Heat-related illness progresses along a spectrum. Catching it early, at the cramp or exhaustion stage, is far easier to treat than catching it late. Heat stroke is a medical emergency with a significant fatality rate. The CDC identifies these as the key stages and symptoms.[1]
Heat cramps
Muscle cramps or spasms, usually in the legs or abdomen. Caused by loss of electrolytes through heavy sweating.
Response: Stop activity. Move to a cool place. Drink water or a sports drink with electrolytes. Gently stretch the affected muscles. Do not resume activity until cramps stop completely.
Heat exhaustion
Heavy sweating, cold and clammy skin, fast and weak pulse, nausea or vomiting, tiredness, weakness, dizziness, headache, muscle cramps. Body temperature may be elevated but typically below 104 degrees Fahrenheit. The body is still trying to cool itself.
Response: Move to a cool place. Loosen clothing. Apply cool wet cloths or get in a cool bath. Sip water. If vomiting occurs, vomiting continues, or symptoms worsen, call 911.
Heat stroke
Body temperature of 103 degrees Fahrenheit or higher. Hot skin that may be red, dry, or damp. Fast, strong pulse. Confusion, slurred speech, altered mental state. Loss of consciousness. The body has lost the ability to regulate temperature.
Response: Call 911 immediately. This is a medical emergency. Move the person to a cool place. Begin rapid cooling: cold water immersion if possible, cold wet cloths, ice packs to the neck, armpits, and groin. Do not give fluids to an unconscious person. Do not delay cooling while waiting for EMS.
Check On These People
Who is most at risk
Not everyone faces the same risk during a heat-related outage. Some people's bodies are less able to regulate temperature. Some take medications that impair sweating or hydration. Some live alone with no one to check on them. Knowing who in your household and neighborhood falls into these categories determines how urgently you need to find a cool environment.
Adults over 65
Aging reduces the body's ability to sense heat, regulate temperature, and trigger thirst. The CDC notes that people over 65 account for a disproportionate share of heat-related deaths. Check on elderly neighbors and family members at least twice daily during a heat-related outage.[2]
Infants and young children
Children's bodies produce more heat relative to their size and sweat less efficiently than adults. They depend on caregivers to manage their environment. Keep infants in the coolest room, dress them in minimal clothing, and offer fluids frequently.
People on heat-sensitive medications
Diuretics reduce fluid volume. Beta-blockers limit heart rate response to heat. Anticholinergics reduce sweating. Some psychiatric medications affect temperature regulation. If anyone in your household takes these medications, finding a cool environment is urgent, not optional.[3]
People with chronic conditions
Heart disease, diabetes, respiratory conditions, and kidney disease all reduce the body's capacity to handle heat stress. People with these conditions should have a plan for where to go during a prolonged heat-related outage before the outage occurs.
People who live alone
A person living alone who develops heat exhaustion may not recognize the progression to heat stroke. Confusion is a hallmark symptom, and a confused person cannot call for help. Agree with a neighbor, friend, or family member to check in by phone or in person at set times during a heat event.
Pets
Dogs and cats can overheat quickly. Ensure pets have access to cool water at all times. Move their resting area to the coolest part of the house. Signs of heat stress in dogs include excessive panting, drooling, lethargy, and unsteady movement. In cats: panting (unusual for cats), lethargy, and drooling.
Protect What Matters
Medications, food, and insulin
Heat does not just affect people. Some medications lose effectiveness when stored above their recommended temperature range (typically 68 to 77 degrees Fahrenheit). Food spoils faster. Insulin degrades.
Temperature-sensitive medications
Insulin, some heart medications (nitroglycerin), thyroid medications, and epinephrine auto-injectors (EpiPens) are sensitive to heat. If your refrigerator is off and room temperature is rising, place these medications in a cooler with ice packs. Do not place them directly on ice, which can freeze and damage some medications. A small insulated bag with a single ice pack, kept in the coolest room, can maintain a safe range for hours.
Refrigerated food
A closed refrigerator holds its temperature for about 4 hours during a power outage. A full freezer holds temperature for about 48 hours (24 hours if half full). Do not open the doors unnecessarily. If the outage will last longer than 4 hours, move perishables to a cooler with ice. Our refrigerator during outages guide covers food safety timelines in detail.
Water supply
During heat events, water consumption increases significantly. An adult may need a gallon or more of drinking water per day in sustained heat, compared to the standard recommendation of half a gallon for normal conditions. If your water supply depends on an electric well pump, a power outage means no water. Have stored water available. Our water preparedness section covers storage and backup options.
The Decision
When home is not safe
Sometimes the right answer is to leave. If your home is dangerously hot, passive cooling is not enough, and you have vulnerable household members, go somewhere with air conditioning. Make this decision before anyone is in distress, not after.
Decision triggers
Leave if: indoor temperature exceeds 95 degrees Fahrenheit and you cannot bring it down, anyone in the household is showing early signs of heat exhaustion, a vulnerable person (elderly, infant, chronic condition, heat-sensitive medication) is present and the outage is expected to last through the night, or the heat index outside exceeds 105 and your home has no passive cooling options. Make this decision while transportation is still safe and daylight is available.
Cooling centers
During heat emergencies, many communities open public cooling centers in libraries, community centers, senior centers, and houses of worship. Check with your local emergency management office, call 211, or monitor local news for locations and hours. Plan your route before you need it. If a household member cannot be moved easily, call 211 or your local emergency management office for assistance.[8]
Alternative locations
Shopping malls, movie theaters, restaurants, and large retail stores all have air conditioning and backup power. A family member or friend's home in a neighborhood with power may be the simplest option. Even spending a few hours in a cool environment and returning home in the evening can be enough to prevent heat illness and reset your body temperature.
Before the Next Outage
Building your cooling backup
The best time to prepare for a heat-related outage is before summer starts. These measures cost relatively little and make a large difference.
Battery-powered fans
Keep at least one rechargeable fan and one set of backup batteries or a USB battery pack. A small clip-on fan can make a sleeping area bearable. A larger rechargeable floor fan can cool a room. Charge them when you hear a heat wave forecast. Remember: fans help only below 90 degrees Fahrenheit. Above that, they are only useful if combined with skin wetting.
Reflective window treatments
Reflective window film, exterior shade screens, or even emergency blankets taped to the inside of windows can reduce solar heat gain by 50 to 80 percent. Installing these before summer is far easier than doing it during an outage. Renter-friendly options include static-cling reflective film that peels off without damaging the glass.
Indoor thermometer
A simple indoor thermometer placed in your designated cool room gives you the objective data you need to make the stay-or-leave decision. Without one, you are guessing. Digital thermometers with humidity readings are available for under ten dollars and run on a coin battery that lasts a year or more.
Portable power station
A battery-based power station of 500 Wh or more can run fans, charge phones, and power a small window AC unit for a limited time. Our portable power station guide covers sizing. Our measuring power use guide shows how to know what your specific devices draw.
Frozen water bottles
Keep several gallon jugs of water in the freezer. They extend food safety by keeping the freezer cold longer during an outage, and once partially thawed, they double as personal cooling packs and safe drinking water. This costs nothing and takes five minutes to set up.
Know your cooling center plan
Identify where cooling centers are in your area before you need them. Know the transportation options. If you rely on public transit, know whether transit operates during power outages. If a household member cannot be moved easily, call 211 or your local emergency management office for assistance.
Sources
- CDC. "About Heat and Your Health." cdc.gov. Accessed September 2026.
- CDC. "Older Adults and Extreme Heat." cdc.gov. Accessed September 2026.
- CDC. "Heat and Medications: Guide for Clinicians." cdc.gov. Accessed September 2026.
- NWS/NOAA. "Heat: The Number One Weather Killer." weather.gov. Accessed September 2026.
- CPSC. "Portable Generator Safety Tips." cpsc.gov. Accessed September 2026.
- EPA. "Extreme Heat and Indoor Air Quality." epa.gov. Accessed September 2026.
- Gagnon D, et al. "Electric Fan Use in Older Adults During Heat Waves." JAMA Network Open, 2025. jamanetwork.com. Accessed September 2026.
- Ready.gov. "Extreme Heat." ready.gov. Accessed September 2026.
Keep Going
Related guides
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Techniques that work without any equipment, from cross-ventilation to thermal mass.
Power outage action plan
The complete step-by-step for the first hour, first day, and extended outage.
Heating during outages
The winter counterpart: safe indoor heat, CO safety, pipe protection, and hypothermia recognition.