Power Outage During Extreme Heat: What to Do When the AC Stops

A power outage during extreme heat is more than an inconvenience. When electricity fails during a heat wave, air conditioning stops, indoor temperatures can rise, phones and essential devices begin losing charge, and some households may quickly face a heat emergency.

If your home experiences an AC outage during dangerous summer temperatures, the priority is not keeping every appliance running. The priority is keeping people cool, hydrated, informed, and ready to move somewhere safer if the house becomes too hot.

This guide explains how to stay cool during a power outage, when a fan may not be enough, how to use backup power safely, and how to prepare for a summer power outage before the next heat wave arrives.

Quick Answer: What Should You Do When the AC Stops?

When the power goes out during extreme heat, close blinds and shades to reduce incoming sunlight, move to the coolest area of the building, drink water, reduce physical activity, wear lightweight clothing, and use cool water to lower body temperature.

If your home continues getting hotter, do not rely indefinitely on a fan or emergency cooling equipment. Identify an air-conditioned cooling center, library, community building, shopping center, or another safe place you can reach.

The National Weather Service recommends these measures specifically for dangerous heat combined with a power outage.

Why Is a Summer Power Outage More Dangerous?

A normal power failure may mean a few hours without lights, internet, or appliances.

A summer power outage during a heat wave creates another problem: your main source of indoor cooling can disappear when you need it most.

As the home heats up, people may have difficulty lowering their body temperature. The risk can be greater for older adults, children, people with chronic health conditions, people living alone, and anyone who relies on electricity-powered medical devices or refrigerated medication.

CDC's HeatRisk guidance specifically notes that power outages during major heat events can affect people who rely on powered medical equipment or temperature-sensitive medication.

That makes extreme-heat preparedness different from ordinary power failure preparation.

What to Do During the First 30 Minutes of a Power Outage

The beginning of an outage is the best time to organize your household before indoor conditions become more difficult.

Situation	Immediate action
Power has just failed	Check your utility and official emergency alerts
Sunlight is heating rooms	Close blinds, shades, and curtains
Indoor temperature is rising	Move to the coolest practical room
You feel overheated	Drink water and cool your skin
Phones are losing power	Activate battery-saving mode
Home keeps becoming hotter	Prepare to move to air conditioning
Someone becomes confused or collapses	Call 911 and begin cooling

Avoid unnecessary physical activity and do not wait until the home becomes extremely uncomfortable before thinking about an alternative cooling location.

A good extreme heat power outage safety plan should already identify where household members can go if home cooling fails.

How to Stay Cool Without AC During a Power Outage

If you are wondering how to stay cool without AC, begin by reducing the amount of heat entering your home.

Keep blinds, curtains, and shades closed on windows exposed to strong sunlight. Move to a lower or more shaded area of the building when that space is cooler.

Avoid using heat-producing appliances unnecessarily.

Then focus on cooling your body rather than trying to cool the entire building.

A cool shower or bath can help. You can also apply a damp, cool cloth or use cool water on exposed skin. Wear loose, lightweight clothing and reduce strenuous activity.

The National Weather Service recommends staying hydrated, moving to the coolest part of the home, using cool water to lower body temperature, and finding air conditioning when necessary during a power outage during dangerous heat.

These simple actions can form part of an effective emergency cooling strategy, but they should not replace relocation when indoor conditions become unsafe.

Are Fans Safe During Extreme Heat?

A battery-powered or rechargeable fan can be useful during an AC outage, but a fan does not automatically make a dangerously hot room safe.

Current CDC guidance says fans can be used for body cooling when indoor temperatures are below 90°F. At indoor temperatures above 90°F, CDC warns that a fan can increase body temperature.

That is why a battery-powered fan for a power outage should be treated as one cooling tool—not as a replacement for air conditioning.

If indoor temperatures continue climbing, look for an air-conditioned location instead of assuming stronger airflow will solve the problem.

When Should You Leave a Home Without AC?

There is no single number of hours that tells everyone how long they can safely remain in a house without air conditioning.

Risk depends on indoor temperature, humidity, age, health conditions, medications, mobility, hydration, building design, and how long the outage is expected to last.

Instead, ask:

Can everyone in this household still remain safely cool?

If the answer is becoming uncertain, moving somewhere with working air conditioning is safer than waiting for obvious heat illness.

CDC advises using air conditioning or locating a place that has it and notes that even a few hours in a cool location can reduce health risks from heat. Cooling centers may be available through local emergency-management or health agencies, and many areas provide information through 2-1-1.

Knowing your nearest cooling location before a heat emergency can make that decision much easier.

Know the Signs of Heat Exhaustion

Heat exhaustion can develop when the body loses too much water and salt through sweating.

Possible symptoms include headache, nausea, dizziness, weakness, irritability, thirst, heavy sweating, elevated body temperature, and reduced urine output.

Move the person away from the hot environment and begin cooling them. Remove unnecessary clothing, use cool compresses or cool water, and encourage frequent sips of cool water when appropriate.

Seek medical attention when symptoms are severe, worsening, or you are unsure about the person's condition.

Heat Stroke Is a Medical Emergency

Heat stroke is much more serious.

Symptoms can include confusion, altered mental status, slurred speech, loss of consciousness, seizures, very high body temperature, and hot skin that may be dry or accompanied by heavy sweating.

If heat stroke is suspected, contact emergency services right away.

Move the person to a cooler area and begin rapid cooling while emergency medical help is coming. CDC recommends cooling methods such as wetting the skin, applying cold wet cloths, soaking clothing with cool water, or cold-water or ice-water immersion when possible.

Do not allow concerns about the electricity outage, equipment, or property to delay emergency medical treatment.

What Should You Power First During an Extreme Heat Power Outage?

Having backup power helps most when you decide in advance what actually needs electricity.

Communication devices are often an early priority. Phones may be needed for emergency alerts, utility information, family communication, maps, and contacting help.

Households may also need power for medical equipment, emergency lighting, radios, or other essential devices.

A rechargeable fan may provide useful emergency cooling when indoor conditions remain appropriate for fan use.

Air conditioning demands more careful planning than most other power needs.

Do not assume a normal phone power bank or small battery pack can operate a window air conditioner or central HVAC system. Cooling equipment can have significant running and startup power requirements.

Before an emergency, compare the appliance's electrical requirements with the backup system's rated continuous output, surge capability, and usable battery capacity.

Can a Power Bank Run an Air Conditioner?

Usually, a standard phone-sized power bank should not be considered an air-conditioning backup.

Power banks are much better suited to smaller devices such as phones, radios, USB lights, and some small fans.

Larger portable power stations may operate certain appliances, but compatibility depends on the appliance's wattage, startup demand, power station output, battery capacity, and expected runtime.

Never estimate critical backup power for an air conditioner from battery capacity alone.

Check both the appliance specifications and the power system manufacturer's limits before relying on that setup during an emergency.

Generator Safety During a Power Outage

Generators can provide considerably more emergency power, but they introduce a serious carbon-monoxide risk when used incorrectly.

FEMA says generators, camp stoves, and charcoal grills should be operated outdoors and at least 20 feet away from building openings such as windows, doors, and garages.

Never operate a portable generator inside a home, garage, basement, shed, or other enclosed or partially enclosed area.

Homes using generators should also have working carbon-monoxide alarms.
Generator safety during a power outage should always come before convenience.
Backup power should reduce emergency risk—not create another emergency.

Keep Your Phone Working During a Summer Power Outage

When power disappears, avoid wasting phone battery during the first few hours.

Switch on battery-saving mode, reduce screen brightness, disable unnecessary background activity, and reserve portable chargers for important communication.

Check official utility and emergency-management information while communication services remain available.

A radio or other independent information source can provide an additional layer of preparedness if cellular service or internet access becomes unreliable.

Having multiple ways to receive emergency information is particularly useful during prolonged summer outages, storms, wildfires, and other events that can affect communications infrastructure.

Food Safety During a Summer Power Outage

Keep refrigerator and freezer doors shut as much as possible to help preserve the cold air inside.

FEMA guidance says a refrigerator can keep food cold for about four hours without power, while a full freezer can stay at a safe temperature for about 48 hours when kept closed.

A refrigerator or freezer thermometer can help determine whether food remains at a safe temperature.

Do not rely only on appearance or smell when determining food safety.
Most importantly, never remain in a dangerously hot home simply because you are trying to protect refrigerated food.

People come first.

Build a Heat-Wave Emergency Kit Before the Power Goes Out

A useful heat-wave emergency kit should support hydration, communication, safe lighting, cooling, essential medical needs, and relocation.

Consider drinking water, flashlights, charged power banks, charging cables, an emergency radio, a battery-powered fan for appropriate conditions, a thermometer, necessary medications, printed emergency contacts, and any household-specific medical supplies.

FEMA also recommends keeping electronic devices charged before an outage and planning alternative power sources that can recharge them.

Check your emergency equipment periodically.

A power bank stored at zero charge or a flashlight with dead batteries will not provide much help when an actual heat emergency begins.

Common Summer Power Outage Mistakes

One of the biggest mistakes is waiting until someone develops symptoms before looking for air conditioning. Plan ahead and identify a safe place you can go if needed.

Another is assuming any fan will keep you safe regardless of indoor temperature. CDC's current guidance places an important limitation on fan use above 90°F indoors.

Do not drain all your emergency power immediately. Preserve enough capacity for communication and other essential needs.

Do not assume owning emergency equipment means you are prepared. Batteries need charging, flashlights need checking, and backup systems should be tested before an outage.

And never place a generator inside or close to doors, windows, garages, or other building openings.

Frequently Asked Questions

What are the best ways to keep cool when the power goes out?

Close blinds and shades, move to the coolest practical area of the building, avoid strenuous activity, drink water, wear lightweight clothing, and cool your skin with cool water. If the home continues heating up, move to an air-conditioned location rather than relying only on household cooling methods.

How can you cool a house without electricity?

Start by blocking direct sunlight and reducing indoor heat sources. Use the coolest rooms available and focus on cooling people directly with cool showers, baths, damp cloths, and appropriate fan use. If the building becomes dangerously hot, leaving for an air-conditioned location may be safer than trying to cool the entire house.

Can a fan keep you safe when the AC stops?

Not in every situation. CDC currently advises using fans for body cooling when indoor temperatures are below 90°F and warns that fans can raise body temperature above that level. Air conditioning or another safe cooling location becomes increasingly important as indoor temperatures rise.

How long can you stay in a house without AC during a heat wave?

There is no universal safe time limit. Indoor temperature, humidity, health, age, medications, mobility, and access to water and cooling all affect risk. Monitor household members and indoor conditions. If people cannot remain safely cool, relocate rather than waiting for a fixed number of hours.

What should you do if someone has a heat stroke during a power outage?

Call 911 immediately. Move the person to a cool area and begin rapid cooling while emergency medical services are coming. Confusion, altered mental status, seizures, loss of consciousness, or very high body temperature are major warning signs.

What backup power should you have for an extreme heat emergency?

That depends on what must remain operational. Phone charging, emergency communication, lighting, medical equipment, and appropriate small cooling devices may have very different power requirements. Identify essential loads first and then choose backup equipment capable of supporting them safely.

Final Recommendation

A power outage during extreme heat should be treated primarily as a health and cooling problem—not simply a loss of electricity.

When the AC stops working during a heat wave, reduce heat entering the home, keep people hydrated, use safe emergency cooling methods, preserve communication, and monitor everyone for signs of heat illness.

Use backup power strategically rather than trying to keep every appliance operating.

Most importantly, knowing when staying home is no longer the safest option.
Before the next summer power outage, make sure your household knows where to find air conditioning, how to receive emergency information, what equipment must remain powered, and how you will safely leave the home if indoor conditions become dangerous.

A well-prepared heat emergency plan gives you something more valuable than a pile of emergency gear: a clear decision about what to do when the power goes out and the temperature keeps rising.