Heat exhaustion vs heat stroke

A man walked off the Duval crawl and into my clinic one July afternoon, soaked through, sheet white, and genuinely puzzled that the bottle of water in his hand had stopped fixing anything. He had heat exhaustion, and he was lucky, because he was still the kind of patient who can be puzzled. Here is the whole column in three sentences. Heat exhaustion is your body still coping: sweating hard, feeling terrible, begging you to stop. Heat stroke is the cooling system failing, the brain overheating, and the puzzlement turning into confusion. Exhaustion gets shade, water, and rest. Stroke gets 911, immediately, while you cool the person with everything you have.

Coping versus failing, side by side

Heat exhaustion looks like a body working desperately and succeeding, barely: heavy sweating, nausea, dizziness, a pounding headache, clammy skin, weakness, maybe a fainting spell that resolves in the shade. Miserable, and still coping. Heat stroke looks like the machinery giving out: confusion, slurred speech, strange behavior, stumbling, skin that may be hot and dry or may still be sweating, then collapse or a seizure. Per the CDC's extreme heat guidance, heat stroke is defined by a core temperature of 104°F, which is 40°C, together with a change in brain function. That second half is the tell you can use on a beach without a thermometer: when the person stops making sense, the emergency has already started.

Teach it to your group this way on the drive down: sweating and miserable is coping, confused is failing. You will not remember a symptom table at mile marker zero in August. You will remember that.

Stop, cool, call

1. Stop the activity. Not after this song, not after the parasail. Now.
2. Move to shade or air conditioning, whichever is closer.
3. Cool aggressively: water on the skin, ice or cold cans against the neck, armpits, and groin, wet shirts, anything.
4. Small sips of water if the person is fully alert and can hold the bottle themselves.
5. The moment thinking changes, call 911. Keep cooling the entire time you wait.

For exertional heat stroke, the runner or the bike tourist who went down hot, cold water immersion is the gold standard while EMS is on the way: the American College of Sports Medicine's position stand on exertional heat illness (2007, reaffirmed in its 2023 consensus statement) and the Korey Stringer Institute both put whole-body cold water first, because it produces the fastest cooling rates and the best survival. A kiddie pool, a bathtub, the shallows at Fort Zach with someone supporting the head: cool first, transport fast.

The number that decides your afternoon is the heat index, not the thermometer, and the National Weather Service heat index scale marks the danger band at 103°F, a line Key West crosses routinely in summer. The live number is in the header of this page, and the longer reading lives at this week on the island.

The myths, retired

First myth: you always stop sweating in heat stroke. No. Classic heat stroke victims often do have hot, dry skin, but exertional cases are frequently still drenched when their brain starts failing. Waiting for dry skin wastes the minutes that matter most. Second myth: push through it and you will toughen up. Acclimatization is real, but per the ACSM it takes ten to fourteen days of graded exposure, which is longer than most vacations. You cannot earn it by suffering on day two. Third myth: beer counts as fluids. It counts against. Alcohol dehydrates you while the sun does the same, a double bill I cover properly in the dehydration column.

Recovery, honestly

Heat exhaustion, treated with rest, fluids, and a cool room, typically resolves over 24 to 48 hours. Respect the second half of that sentence: the day after is not a bonus beach day, because your heat tolerance stays lowered for days after the episode, and the second round starts from a worse position. Heat stroke is a different contract entirely. A survivor needs a medical evaluation and clearance before going back into the heat at all, and the organ systems that took the hit get to vote on the timeline. And if heat exhaustion is not clearly improving after an hour of real cooling and real fluids, stop managing it from a towel. Working out where to be seen on the island today is keywesthealthcare.com's whole job.

Who this bites hardest

Visitors in their first 48 hours, before their bodies have understood what latitude they are at. Older adults, whose thirst signal and sweat response both run late. Anyone on diuretics or beta blockers, which quietly limit the body's coping tools. And, in a category all their own, people drinking in the sun, which on this island describes a demographic visible from space. The rental bikes with no shade, the sandbar with no clock, and the second mojito are each fine ideas separately. Summer stacks them.

Questions from the beach

Sources

• CDC extreme heat guidance (heat stroke at 104°F core temperature with neurologic change).
• National Weather Service heat index scale (danger band from 103°F; Key West summer heat indexes run past 100 per NWS Key West).
• American College of Sports Medicine, position stand on exertional heat illness, 2007, and the ACSM expert consensus statement on exertional heat illness, 2023 (cold water immersion first line; acclimatization ten to fourteen days).
• Korey Stringer Institute, exertional heat stroke guidance (cool first, transport second).