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Key takeaways

• Heat is one of the deadliest weather hazards in the U.S. — in an average year it kills more Americans than hurricanes, tornadoes, or floods (National Weather Service).
• Water first. Store at least one gallon per person per day and drink steadily, before you feel thirsty (Ready.gov).
• Have a cool place to go. If the AC fails, a public cooling center beats riding it out — fans alone don't prevent heat illness in the high 90s°F and above (CDC).
• Know the signs of heat stroke — body temp 103°F+, hot dry or damp skin, confusion. Call 911 (CDC).
• Check on the people most at risk — older adults, young kids, and anyone without air conditioning.

Extreme heat doesn't look like a disaster — no wind, no floodwater, no warning siren — but in an average year it quietly kills more Americans than any other weather hazard (NWS). The danger spikes when a heat wave overloads the grid and the air conditioning goes out with the power. This extreme heat preparedness checklist is a practical heat wave safety kit and plan: what to stock, how to stay safe during a heat wave power outage, and what to do in extreme heat when your home stops cooling.

What should be in an extreme heat emergency kit?

A heat kit is built around hydration, cooling, and a powerless backup — not the flashlights-and-canned-food list people picture.

Water and hydration

• At least one gallon of water per person per day, with extra for pets (Ready.gov).
• Electrolyte packets or sports drinks — you sweat out salt as well as water, and replacing only water isn't enough.

Cooling without AC

• Battery-powered or rechargeable fans and a power bank to run them.
• Cooling towels, cold packs, or a spray bottle for evaporative cooling.
• Light-colored, loose, lightweight clothing and a wide-brim hat.
• A thermometer to track indoor temperature — upper floors can run 10°F+ hotter than the forecast.

Protection and medications

• Sunscreen (SPF 30+) and sunglasses.
• A note of any medications that lose potency in heat (some need cool storage) and a cooler to hold them during an outage.

Have a plan, not just a box

• The address of your nearest public cooling center, library, or mall (Ready.gov).
• A charged power bank so your phone can keep receiving alerts.

How do you stay safe during a heat wave power outage?

This is where heat waves turn deadly — when the grid fails under air-conditioning demand and homes turn into ovens. The CDC's guidance is direct: once it's in the high 90s°F, an electric fan won't prevent heat illness — it just circulates hot air (CDC). So:

• Leave for a cooler place. A cooling center, library, store, or a friend's house with power is safer than toughing it out (Red Cross).
• Drink water steadily even when you're not thirsty, and skip alcohol and caffeine.
• Take cool showers or baths to bring your core temperature down.
• Stay on the lowest floor, blinds closed against the sun.
• Never sit in a parked car, and never leave children or pets in one — interior temperatures climb to lethal levels within minutes.
• Check on neighbors — most heat deaths are older adults living alone.

What are the warning signs of heat stroke?

Knowing heat exhaustion from heat stroke can save a life. Per the CDC:

• Heat exhaustion — heavy sweating; cold, clammy skin; dizziness; nausea; headache; a weak, fast pulse. Move to a cool place, sip water, loosen clothing, and apply cool cloths.
• Heat stroke (call 911) — body temperature 103°F or higher, hot red skin that's dry or damp, a fast strong pulse, confusion, slurred speech, or fainting. Move the person somewhere cool and cool them with water while you wait — don't give fluids if they're confused or unconscious.

Heat stroke is a medical emergency. When in doubt, call 911.

Heat advisory vs. excessive heat warning

The National Weather Service uses tiered alerts (NWS heat safety):

• Heat Advisory — dangerous heat is expected. Limit outdoor exertion and hydrate.
• Excessive Heat Warning — more extreme, life-threatening heat. Stay indoors in air conditioning, check on the vulnerable, and treat it as the emergency it is.

When either is issued, move outdoor work to early morning and don't assume you'll "tough out" the afternoon.

Which cities face the highest extreme-heat risk?

If you live somewhere that bakes in summer, heat — not storms — may be the hazard most likely to send someone you love to the ER. Phoenix is the hottest major city in the U.S.; in 2023, Maricopa County recorded 645 heat-related deaths — the most ever documented — during a stretch of 31 straight days at or above 110°F. Houston pairs brutal Gulf humidity with the post-hurricane outages that make heat deadly, Dallas sees dangerous July–August heat on top of its tornado risk, and Sacramento endures long Central Valley heat waves all summer.

In Dallas, that heat shares the calendar with severe storms — pair this with our tornado emergency kit checklist. And for the basics people overlook in any kit, see the 5 items most people forget in an emergency kit.

Want to know whether extreme heat tops your address's risk list — and exactly what to stock for it? The free 2-minute ReadyAF risk assessment weighs your location's heat and outage risk and builds a kit list tailored to your household, before the next heat wave hits.