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.
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 steps slow the rise.
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.
Open windows on opposite sides for cross-ventilation
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. If there is no breeze, any open window is better than a sealed house, but only if outdoor air is cooler than indoor air. During the hottest part of the day, keeping windows closed with blinds drawn may be better than bringing in 100-degree air.
Move to the lowest floor
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. If you have no basement, the ground floor with blinds drawn is the next best option. Bring water, medications, phone chargers, and anything you need so you do not have to go upstairs.
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.
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]
Without Electricity
Cooling your body without power
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.
Wet towel method
Soak a towel or bandana in cool water and drape it over your neck, wrists, or forehead. As the water evaporates, it pulls heat from your skin. Re-wet it when it warms up. This is simple, requires no equipment, and is surprisingly effective. Focus on pulse points: the neck, wrists, inner elbows, and behind the knees, where blood vessels are close to the surface.
Battery-powered fans
Moving air across skin accelerates evaporation and convective cooling. A battery-powered or rechargeable fan is the single most useful cooling device during a power outage. A small clip-on fan draws 2 to 5 watts. A larger rechargeable floor fan draws 10 to 30 watts. Both can run for hours on a fully charged portable power station or USB battery pack.
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. If your water supply is limited, prioritize drinking water over bathing water.
Clothing and activity
Wear loose, lightweight, light-colored clothing. 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.
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) become more important. This is why hot and humid conditions are more dangerous than hot and dry conditions at the same temperature.
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.
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, 211, or local news for locations. Plan your route before you need it.
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.
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.
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.
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.
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.
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. "Heat-Related Illness: Symptoms and First Aid." cdc.gov. Accessed August 2026.
- CDC. "Older Adults and Extreme Heat." cdc.gov. Accessed August 2026.
- CDC. "Heat and Medications: Guide for Clinicians." cdc.gov. Accessed August 2026.
- NWS/NOAA. "Heat: The Number One Weather Killer." weather.gov. Accessed August 2026.
- CPSC. "Portable Generator Safety Tips." cpsc.gov. Accessed August 2026.
Keep Going
Related guides
Passive heating and cooling
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.