What you’ll learn
- Tell heat exhaustion from heat stroke by the sign that matters
- Cool someone effectively, using the method that actually works fastest
- Know when fluids help and when they are dangerous
- Recognize who is at higher risk before the day gets hot
- Act on the 911 threshold without waiting to be certain
Somebody working outside has gone pale and clammy and wants to sit down. Ten minutes later they're still not right. The question you're actually trying to answer is whether this is the kind of bad that a cold drink and some shade will fix, or the kind that needs an ambulance — and for a while, the two look almost the same.
There's one sign that separates them, and it isn't how hot they feel or how much they're sweating.
The ladder, and how fast it climbs
Heat illness isn't three separate conditions — it's one thing getting worse, and somebody can move up it faster than you expect. That's why catching it early matters more than classifying it perfectly.
Stage | What you see | What to do |
|---|---|---|
Heat cramps | Painful muscle spasms, heavy sweating, thinking clearly | Stop the activity, get to a cool place, rest, electrolyte drink |
Heat exhaustion | Heavy sweating, weakness, nausea, headache, fast pulse, dizziness — still thinking clearly | Cool place, lie down, start cooling, fluids if alert. Escalate if anything changes |
Heat stroke | Confusion, slurred speech, stumbling, seizure or collapse. Skin may be wet OR dry | Call 911 and start cooling immediately. Nothing by mouth |
The line that matters is the last row, and it isn't about temperature — it's about how they're thinking. Anyone who has become confused, slurred, unsteady or strange in the heat has heat stroke until somebody with a thermometer and a hospital proves otherwise.
Cramps and exhaustion
The lower two rungs are the ones you can handle where you are, and handling them properly is what stops the third.
Stop what they're doing — that part isn't optional, and it's the step people negotiate with. Get them somewhere cooler, out of the sun, and get them lying down with their legs up if they're light-headed. Loosen or take off heavy clothing and boots. Start cooling them actively: cool water on the skin, a fan, cold wet towels on the trunk.
If they're alert enough to hold a drink, give them one. And then watch them for the next half hour rather than sending them back to work — the whole point of catching it here is that the next rung is an emergency.
Heat stroke is the 911 one
Call 911. Then start cooling immediately — don't wait for the ambulance, and don't put them in a car to drive them yourself if help is coming.
That ordering is deliberate and it runs against instinct. Every impulse says get them to a hospital, but for heat stroke the minutes spent cooling on the spot matter more than the minutes saved driving. Cooling is the treatment, and it can start where they are lying. Tell the dispatcher what you're doing and they will tell you to keep going.
If they lose consciousness but are breathing normally, put them on their side and keep cooling. If they stop breathing normally, that's CPR — and gasping isn't breathing.
Cooling: cold water beats everything
Immersion is first choice by a distance, and it's worth improvising for — a large cooler, a stock trough, a kiddie pool, a shower. Get as much of them into cold water as you can manage, keeping the head above it.
Ice packs tucked into armpits and groin used to be taught as the main method. They aren't — they cool a small area slowly, and on their own they aren't enough for someone with heat stroke. Use them if that's genuinely all you have, alongside water and air rather than instead of it.
Water, sports drinks, and nothing at all
Water is right for cramps and exhaustion, and electrolyte or sports drinks are better when someone has been sweating hard for hours — plain water alone over a long shift can leave them low on salts.
Salt tablets aren't the answer and haven't been for a long time. A drink with electrolytes in it does the same job without the stomach upset.
Give nothing by mouth to anyone who is confused, drowsy or unconscious. This is the one to hold on to, because offering water is the most natural thing in the world to do for someone in trouble — and someone who can't reliably swallow can inhale it instead.
Risk factors that stack up
Most heat emergencies happen to people who had several of these at once rather than one.
Not being used to it. The first hot week of the year, or a new worker's first days on an outdoor job. Acclimatization takes one to two weeks.
Humidity. Sweat only cools you when it evaporates. At high humidity it just runs off, and the temperature alone understates the danger.
Age at both ends — older adults and small children regulate heat less well.
Some medications and conditions, including for blood pressure, allergies and mental health.
Exertion and gear. Heavy clothing, protective equipment and hard physical work all trap heat.
No shade and no breaks — which is a workplace problem rather than a personal one.
Staying ahead of it
Drink before you're thirsty, take breaks in shade on a schedule rather than when you notice, build up to full work over a week or two in the heat, and keep an eye on each other — people rarely notice their own confusion, which is exactly the sign that matters most.
Put it into practice
Training scenario:
You're running a roofing crew on the second genuinely hot day of the year. It's about two in the afternoon. One of your guys — twenty-four, started Monday, been keeping up all week — comes down the ladder slowly and sits on the tailgate. He's soaked through. He answers you, but he calls you by the wrong name and then laughs about it. Someone hands him a bottle of water. You're two hours from finishing a job that has to be watertight before tomorrow's rain.
Walking it through:
The wrong name. Everything else — soaked, tired, hot afternoon, new on the job — fits exhaustion comfortably, and the sweating actively pulls you toward the reassuring answer. But he isn't thinking straight, and that is heat stroke until a hospital says otherwise. The laugh makes it easier to dismiss, not less serious.
So the water comes back off him. Somebody confused can't reliably swallow, and that bottle is an aspiration risk rather than a kindness. Call 911, get him flat in the shade, strip the gear off, and get cold water onto and around him — a tub, a hose, soaked towels changed constantly, whatever the site actually has. Cool him where he is; the ambulance is coming to you.
And the real difficulty in this scenario isn't clinical. It's that the correct call costs you the afternoon, the job gets wet tomorrow, and you will feel foolish if he perks up in ten minutes. Make it anyway — heat stroke kills people who were walking and talking twenty minutes earlier, and being wrong about the roof is a bad day rather than a funeral.
Medically reviewed by Dr. Mary Williams, RN, DC
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