Heat Exhaustion vs. Heat Stroke: One Is an Emergency — Can You Tell the Difference?

Heat-related illness is the #1 weather-related killer in the United States, according to the CDC. Not hurricanes, not tornadoes — heat. And yet most people either don't know the warning signs or aren't sure what to do when they see them.

The difference between heat exhaustion and heat stroke is not just a matter of degree. One requires rest and cooling. The other requires 911. Getting that call wrong can cost someone their life.

Heat Exhaustion: Serious, But You Have Time to Act

Heat exhaustion happens when your body loses too much fluid and salt through sweating and can't cool itself fast enough. It's a warning — your body is struggling, but it's still fighting.

• Body temperature: Normal to slightly elevated — below 104°F (40°C)
• Skin: Cool, pale, and damp. Heavy sweating is typical.
• Pulse: Fast but weak
• Breathing: Fast and shallow
• Symptoms: Heavy sweating, weakness, dizziness, nausea or vomiting, muscle cramps, headache — and possibly fainting
• Mental state: Normal and alert. The person knows where they are and what's happening.

What to Do

1. Move the person somewhere cool — air conditioning is ideal, shade if AC isn't available.
2. Have them lie down with their legs slightly elevated.
3. Remove excess clothing.
4. Apply cool, wet cloths to the skin — forehead, neck, wrists.
5. If they're conscious and not nauseous, have them sip cool water.
6. Seek medical care if there's no improvement within 30 minutes, or if symptoms worsen at any point.

Heat Stroke: Call 911 Right Now

Heat stroke is what happens when the body's cooling system fails completely. Core temperature spikes to dangerous levels, and organs — including the brain — begin to take damage. This is a medical emergency. Do not drive to the ER. Call 911.

• Body temperature: 104°F (40°C) or higher
• Skin: Hot and red. May be dry, or may still be sweaty — don't use dry skin as your only clue.
• Pulse: Fast and strong
• Breathing: Rapid
• Symptoms: Throbbing headache, confusion, disorientation, slurred speech. May progress to loss of consciousness or seizures.
• Mental state: ALTERED. Confused, delirious, unresponsive. This is the critical sign.

What to Do While You Wait for 911

1. Call 911 immediately. Do this first.
2. Move the person to a cool place.
3. Cool them rapidly — cold water, ice packs applied to the neck, armpits, and groin (where large blood vessels run close to the surface).
4. Do not give fluids to an unconscious person. They can aspirate.
5. Stay with them until emergency services arrive.

The One Sign That Separates Them

If you remember nothing else from this post, remember this: mental status.

If someone in the heat is confused, disoriented, acting strangely, or loses consciousness — that is heat stroke. Call 911. Don't try to manage it on your own.

Who's Most at Risk

Some people's bodies are less able to handle the heat:

• Older adults have a reduced sweating response and may not feel thirst as acutely
• Young children overheat much faster than adults — never leave a child in a parked car, even for a few minutes (temperatures can rise 20°F in under 10 minutes)
• Athletes and outdoor workers are at high risk from exertion in the heat
• People on certain medications — diuretics, antihistamines, some antidepressants — can impair the body's heat response
• Elderly neighbors living alone — check in during heat waves. AC is the single most protective factor against heat illness.

Prevention: The Simple Stuff

• Hydrate before you're thirsty. By the time you feel thirsty, you're already mildly dehydrated. Aim for 8–10 glasses on hot days, more if you're active.
• Wear light, loose, light-colored clothing.
• Avoid the peak heat window: 10am to 4pm. Plan outdoor activity for early morning or evening.
• Never leave children, pets, or elderly adults in parked cars — not even briefly.
• If you don't have AC at home, spend peak hours at a library, mall, or cooling center.