At what temperature is a heat wave dangerous?

The heat index (temperature + humidity combined) matters more than air temperature alone. A heat index above 103°F is dangerous for most people; above 125°F is extreme danger. High humidity at lower temperatures (e.g., 90°F at 90% humidity = heat index of 119°F) can be as deadly as very high dry temperatures. The National Weather Service issues Excessive Heat Warnings when conditions are life-threatening.

What should I do if my power goes out during a heat wave?

Act quickly — a hot home becomes dangerous within hours. (1) Open windows at night to let cool air in; close them in the morning before it heats up. (2) Go to a cooling center, mall, library, or hotel. (3) Visit friends or family who have power. (4) If you must stay home: use battery-powered fans, ice packs, and cooling towels. Stay on the lowest floor. Prioritize any elderly, very young, or medically vulnerable people in the household first.

How much water should I drink during a heat wave?

8 ounces of water every hour you're in the heat — even if you don't feel thirsty. Thirst is a late sign of dehydration. In extreme heat doing physical activity, you may need more. Add electrolytes (sports drinks, electrolyte tablets) if sweating heavily for more than an hour. Warning signs of dehydration: dark urine, dizziness, confusion, no urination for 8+ hours.

Can I use a regular fan to cool down during a heat wave?

Yes, but with an important limitation: fans cool you through sweat evaporation, not by cooling the air. In very high humidity, sweating is less effective, reducing the fan's benefit. More critically: when air temperature exceeds 99°F and humidity is moderate-to-high, fans can actually accelerate heat stress by blowing hot air over your skin. In extreme heat, a cooling center with AC is safer than a fan alone.

What are the warning signs of heat stroke in pets?

In dogs: excessive panting or drooling, reddened gums, vomiting, diarrhea, mental confusion, collapse. Dogs primarily cool through panting; humidity impairs this. In cats: panting (unusual for cats), drooling, lethargy, reddened tongue. Treatment: move to cool area, apply cool (not cold) water to paws and neck, offer small amounts of water, get to a vet immediately. Do not use ice — it can cause vascular constriction and make things worse.

Emergency Planner

Heat Wave Checklist — emergencyplanner.com

https://emergencyplanner.com

Printed: 3/25/2026

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Heat Wave Checklist: How to Prepare for Extreme Heat

Heat Wave Checklist: How to Prepare for Extreme Heat

Heat is the deadliest weather-related killer in the United States, causing more deaths annually than hurricanes, tornadoes, and floods combined. Unlike dramatic weather events, heat waves kill silently — often over several days, disproportionately affecting the elderly, young children, people with chronic illness, and outdoor workers. Preparation before a heat event is the most effective protection.

Last reviewed: 2026-03-01 · Based on Ready.gov, CDC, FEMA guidance

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Cooling Supplies

For home cooling and personal cooling when power or AC fails.

Battery-powered or rechargeable fancritical
A fan without AC provides some relief up to ~100°F — above that, it can make things worse. Know the limit.
CDC ↗
Cooling towels (wet and apply to pulse points: neck, wrists)critical
Reusable cooling towels provide 2–3°F of perceived temperature reduction.
Spray bottle filled with water
Mist skin and let evaporation cool you. More effective with a fan.
Ice packs or DIY: frozen water bottlescritical
Store multiple in the freezer before a heat event. Apply to neck, wrists, and armpits.
Portable air conditioner or window unit
If you don't have central AC. A single-room window unit can create a cooling refuge.
Blackout curtains or reflective window film
South- and west-facing windows can add 10–15°F to a room. Block them before midday.

Hydration

Water: drink before you feel thirsty (8+ oz/hour in heat)critical
Thirst is a lagging indicator of dehydration. Drink proactively during heat events.
CDC ↗
Electrolyte packets or sports drinks
Heavy sweating depletes sodium and potassium. Plain water alone isn't sufficient during prolonged heat.
Avoid alcohol, caffeine, and sugary drinks during heatcritical
These increase dehydration. Save them for cooler parts of the day.
Extra stored water (heat increases daily consumption)critical
Add 50% to your normal stored water quantity for heat scenarios.

Vulnerable Household Members

Heat affects some people faster and more severely.

Check on elderly neighbors and relatives twice dailycritical
Older adults lose the ability to sense heat and sweat less effectively. Most heat deaths are among people living alone.
CDC ↗
Never leave children or pets in parked carscritical
A car interior reaches 140°F within minutes in direct sun. Death can occur in under an hour.
Cooling towels and battery fan for infants and elderlycritical
Infants cannot sweat effectively. Elderly adults lose thermoregulation.
Know heat-related medication interactionscritical
Some common medications (diuretics, beta-blockers, antipsychotics, antihistamines) impair heat tolerance. Ask your doctor or pharmacist.
Pets need water and shade — limit outdoor time to early morning/evening
Ready.gov ↗

Home Preparation

Pre-cool your home before peak heat hours (3–7 PM)critical
Run AC earlier in the day while it's cooler outside. Thermal mass in walls absorbs cool.
Identify the coolest room in your home (usually lowest floor, interior room)critical
During a heat emergency, concentrate in one cool room rather than cooling the whole house.
Know your local cooling centerscritical
Libraries, community centers, and malls open as cooling centers during heat emergencies. Your county emergency management website lists them.
Ready.gov ↗
Weatherstrip doors and windows to retain cool air
Unplug electronics and appliances not in use (they generate heat)

Power Outage During Heat

A heat wave + power outage is a life-threatening combination.

Have a plan for where to go if power fails for 24+ hours in extreme heatcritical
Friend's home, hotel, or cooling center. This plan must be made before the event.
Portable power station to run a fan
A 500 Wh station can run a small fan for 24–48 hours. Far less expensive than a generator.
Know at least two local cooling centerscritical
Minimize oven and stove use during heat (use microwave, grill outside, or cold meals)

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Detailed Guidance

Heat Exhaustion vs. Heat Stroke: Know the Difference

These are two different conditions with different responses: HEAT EXHAUSTION (serious, treat immediately): - Heavy sweating - Cool, pale, clammy skin - Fast, weak pulse - Nausea or vomiting - Muscle cramps - Tiredness and weakness - Dizziness - Headache - Fainting Treatment: Move to cool place. Loosen clothing. Apply cool wet cloths. Sip water. If vomiting or symptoms worsen after 1 hour, call 911. HEAT STROKE (medical emergency — call 911 immediately): - High body temperature (103°F or higher) - Hot, red, dry or damp skin - Rapid, strong pulse - Confusion, slurred speech, unconsciousness - NO sweating despite heat (classic heat stroke) Treatment: Call 911. Cool immediately with cool water immersion, ice packs to neck/groin/armpits, cool spray + fan. Do not give fluids to an unconscious person. The key difference: Heat stroke involves confusion and altered mental status. That's the 911 signal. Source: CDC

Medication Safety in Heat

Many common medications interact with heat in dangerous ways: Medications that IMPAIR heat tolerance (partial list): - Diuretics ("water pills"): increase dehydration risk - Beta-blockers: reduce ability to increase heart rate in response to heat - Antipsychotics and some antidepressants: impair sweating - Antihistamines (Benadryl, etc.): reduce sweating - Stimulants (ADHD medications): increase metabolic heat - Some blood pressure medications If you or a household member takes these medications: 1. Ask your doctor or pharmacist specifically about heat precautions 2. Monitor more frequently during heat events 3. Stay in air conditioning longer than a healthy adult might need to Source: CDC, American Heart Association