The Difference Between Heat Stroke and Heat Exhaustion

One of these is potentially fatal, so knowing their warning signs is crucial.

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Heat exhaustion and heat stroke are both dangerous heat-related illnesses, and while they share some of the same symptoms, there are key differences to be aware of so you know when to seek medical attention.

The precursor to heat stroke, heat exhaustion occurs after exposure to high temperatures and humidity, usually combined with strenuous exercise and lack of adequate hydration. It can happen quickly or over several days.

Heat stroke, on the other hand, is the most severe heat-related illness—and if it's not treated quickly, it can lead to death. There are two main types: traditional heat strokes, which come on gradually and often affect very young and elderly people who can't stay consistently cool (due to lack of air conditioning, for instance). Then there's exertional heat stroke, which mainly affects athletes and anyone else who works or exercises in the heat.

Symptoms of heat stroke vs. heat exhaustion

Heat exhaustion: As a person's body becomes unable to cool itself off, their temperature will rise. Excessive sweating and cold, clammy skin are key signs, along with feeling weak, dizzy, or worried. Headaches, nausea, and a fast but weak heartbeat are also common, James L. Glazer, MD, a family and sports medicine physician told Prevention in a previous interview. Someone experiencing heat exhaustion may even faint.

Heat stroke: A person with heat stroke may stop sweating and have hot, red, dry skin (though this isn't true for everyone—they may still be sweating or have damp skin, especially if you're experiencing exertional heat stroke). Since their body temperature has risen rapidly to 104°F or even higher, they'll often become confused, have trouble walking, complain of a pounding headache, or feel dizzy or nauseous. Their skin will become red, their pulse will become rapid and strong, and they may have trouble breathing or lose consciousness.

What you should do to help

Heat exhaustion: The most important thing is to move them to a cool, shady area or (ideally) an air-conditioned building to prevent their temperature from continuing to rise. Keep them inside—returning to the sun later can cause a relapse. Have them start drinking cool water, rest with their legs slightly elevated if possible, and loosen their clothing. Spray or sponge them with cold water and then fan them, or take a cool bath. Once someone has experienced heat exhaustion, they'll be more vulnerable to heat for about a week afterward, so make sure they take it easy for at least the next seven days.

🚨 If someone's heat exhaustion symptoms worsen, if they're throwing up, or if their symptoms last for more than an hour, call 911 right away as it may be developing into heat stroke, according to the CDC. 🚨

Heat stroke: Call 911 immediately. Heat stroke is a life-threatening condition that requires immediate medical attention. While you wait, move them to a cooler area and try to cool them down as much as possible. If you can, fill a tub with ice water and have them soak for 15 to 20 minutes, or you can hose them down with cold water or take them to a nearby lake or river. You can also place ice packs or cool towels on their head and body. Have them drink water or a sports drink like Gatorade if they're conscious and not too irritable or confused.

How you can prevent heat-related illness

The thought of heat stroke or even heat exhaustion can be frightening, but don't let that keep you from enjoying your summer. A few best practices will help stay cool and hydrated when the weather gets steamy:

☀️ Keep water close and drink it often: You should be drinking about one cup of water for every 15 minutes outdoors, according to the Occupational Safety and Health Administration.

☀️ Don't work out in hot, humid weather: Instead, exercise indoors or move your routine much earlier or later in the day.

☀️ Drink sports drinks with electrolytes: They help rapidly rehydrate the body, especially after an intense workout.

☀️ Avoid alcohol the night before: This isn't news, but booze will dehydrate you even more quickly.

☀️ Give yourself time to acclimate: If you've traveled somewhere much hotter than your normal environment.

☀️ Pay attention to weather warnings: If there's a sweltering heat wave hitting your area, it's not the right day to do yard work or run a few miles around the neighborhood.

☀️ Dress appropriately: Wear loose, light-colored clothing (don't go bare-chested) and don a hat to shade your head and neck.

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