Heat Exhaustion vs. Heat Stroke
In 10 minutes you'll know the difference between heat exhaustion and heat stroke, and how to cool someone down fast.
Print this course — or save it as a PDF from the print dialog. Good for a fridge, a glovebox, or a waiting room.
Why this matters
Heat illness moves along a spectrum, and the far end of it is a genuine emergency. Every summer, extreme heat sends people to emergency rooms and, in its most severe form, kills people who could have been saved by fast cooling (Centers for Disease Control and Prevention). The one sign that changes everything is confusion — and the one action that changes the outcome is cooling someone down before the ambulance even arrives.
Know the signs
Heat exhaustion: the warning stage
Heat exhaustion is the body struggling to cool itself down. Look for heavy sweating, weakness, nausea, headache, and feeling faint or dizzy in the heat. It is uncomfortable and can feel alarming, but it usually responds well to quick action.
Move the person to shade or air conditioning, have them sip water, and apply cool, wet cloths to their skin. Loosen tight clothing. Most people feel noticeably better within 30 minutes. Older adults, people on certain medications, athletes, and outdoor workers are especially prone to heat exhaustion, so check on them first during a heat wave.
Heat stroke is a 911 emergency
Heat stroke happens when the body's cooling system fails completely, and it is life-threatening. The warning sign that changes everything is confusion or acting strangely — slurred speech, stumbling, agitation, or not making sense. That is heat stroke, not exhaustion, and it means call 911 immediately.
Other signs include passing out, a very fast heartbeat, and, if you can measure it, a temperature of 103°F or higher. If heat exhaustion symptoms have not improved after 30 minutes of cooling, or the person starts vomiting, treat it as an emergency and call 911 too.
Hot skin can be dry or sweaty
Many people learn that heat stroke skin is always hot and dry, and that if someone is still sweating, it must be "just" heat exhaustion. That is not reliable. In heat stroke, skin can be hot and dry, or hot and still sweaty — especially in people who were exercising or working hard right before they collapsed.
Do not use sweating alone to rule out heat stroke. The signs that matter most are confusion, passing out, and skin that is hot to the touch. If those are present, treat it as heat stroke no matter how the skin feels.
Cool them down before EMS arrives
For heat stroke, cooling starts the moment you recognize it — do not wait for paramedics. Call 911, then move the person to shade or indoors, and strip off extra layers of clothing.
Apply cold water or ice packs to the neck, armpits, and groin, where blood vessels sit close to the skin. Wet their skin down and fan it if you can. If a cold tub or hose is available, immersing them (keeping the head above water) cools even faster. This is not a wait-for-the-ambulance situation: cooling someone down in the minutes before EMS arrives is what saves lives.
Never leave anyone in a parked car
A parked car can climb past 120°F within minutes, even with the windows cracked and even on a mild day. Never leave a child, an older adult, a pet, or anyone else in a parked car, not even "just for a minute."
If you see a child or a vulnerable person alone in a hot car and they appear distressed, call 911 right away. This single habit — always checking the back seat, never assuming "just a minute" is safe — prevents some of the most tragic heat deaths every year.
How it really looks
The roofer who stopped sweating
Ravi has been roofing since sunrise, and by early afternoon his coworker notices he's stopped making sense — answering questions with the wrong words, fumbling with his tools. His skin is hot, and oddly, he has stopped sweating even though it's 97°F. His coworker doesn't wait to see if a water break fixes it. He calls 911, gets Ravi into the shade, pulls off his shirt, and packs ice from the cooler against his neck and armpits while they wait. Paramedics arrive eleven minutes later and tell him the fast cooling likely kept Ravi's brain from serious damage.
Grandma is just tired, until she isn't
During a heat wave, Josefina's grandson stops by and finds her slumped in her chair, saying she's just tired and wants to be left alone. Her air conditioner broke a week ago. She's sweating heavily, weak, and a little confused about what day it is. He doesn't argue with her about whether it's serious. He moves her to the coolest room, gives her small sips of water, and lays a cool wet towel across her neck while he calls her doctor's after-hours line. When her confusion doesn't clear after twenty minutes, he calls 911 instead. She is treated for heat exhaustion that was sliding toward something worse.
What to do until help arrives
- Watch for confusion or strange behavior. That is the sign that means heat stroke, not simple heat exhaustion.
- Call 911 right away for confusion, passing out, or hot skin — don't wait to see if it passes.
- Move them to shade or air conditioning immediately.
- Strip off extra clothing and apply cold water or ice packs to the neck, armpits, and groin.
- Sip water if they are fully awake and able to swallow; do not force fluids on someone who is confused.
- Keep cooling them until paramedics take over — don't stop once you've called 911.
Myths & mistakes
People often think you can tell heat stroke from heat exhaustion because heat stroke skin is always hot and dry.Actually skin can be hot and sweaty in heat stroke too, especially in someone who was just exercising. Confusion and passing out are the signs that matter most, not how the skin feels.
People often think it's fine to leave someone in a parked car for just a minute or two.Actually a parked car can climb past 120°F within minutes, even with the windows cracked. That is long enough to be deadly for a child, an older adult, or a pet.
People often think heat exhaustion just needs some rest and it will pass on its own.Actually heat exhaustion needs active cooling and fluids, and it can slide into heat stroke if it isn't improving. If it hasn't gotten better in 30 minutes, treat it as an emergency.
What you learned
- Confusion or strange behavior in the heat means heat stroke, not exhaustion — and it means call 911.
- Heat stroke skin can be hot and dry, or hot and still sweaty. Sweating does not rule it out.
- Cool aggressively before EMS arrives: shade, stripped layers, and cold packs to the neck, armpits, and groin.
- Heat exhaustion improves with cooling and fluids within about 30 minutes; if it doesn't, treat it as an emergency.
- Never leave anyone, especially a child, in a parked car — even for a minute.
Sources
- Centers for Disease Control and Prevention — Extreme heat: warning signs and prevention of heat-related illness
- American Red Cross — Heat-related illness: recognizing and responding to heat exhaustion and heat stroke
Spot an error? Tell us — accuracy matters more to us than being fast.
Common questions
Should I give someone with heat stroke water to drink?
Only if they are fully awake, alert, and able to swallow safely. If they are confused, drowsy, or vomiting, do not give anything by mouth — call 911 and focus on cooling their skin with water, ice packs, or a cool cloth instead.
How do I know if it's heat exhaustion or heat stroke?
The clearest sign is mental state. Someone with heat exhaustion is tired and uncomfortable but still thinking clearly. Someone with heat stroke is confused, acting strangely, or passes out. If you see any change in how they are thinking or behaving, treat it as heat stroke and call 911.
Is it ever okay to leave a child in the car with the AC running while I run inside?
No. Cars can overheat dangerously fast if the air conditioning shuts off or fails, and a few minutes is enough for a child's body temperature to climb to a dangerous level. Always take children with you, even for a quick errand.
Check what you know
Five questions. Four correct to pass. Retake as many times as you like — this is practice, not a test.
Keep going
This course belongs to Everyday Emergencies. Courses that pair well with it:
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