It’s a hot summer day, and everything seems normal — you’re enjoying time outside, soaking up the vitamin D with family members or neighbors when suddenly, something starts to feel very, very wrong.

You start to feel confused — maybe someone asked you a question and for some reason, you can’t quite form a complete sentence. Maybe you went inside to cool off and become actually lost in a building you know quite well. Next, you start to feel dizzy or light-headed. This will likely be accompanied by a headache or nausea. The most confusing aspect is that while you might be aware that your symptoms are caused by the heat, you won’t be sweating at all.

If you start to experience this feeling, seek help immediately: You’re experiencing signs of heatstroke. Heatstroke happens when your body’s temperature exceeds 103 degrees Fahrenheit (7 degrees above a normal 96 degrees Fahrenheit), and is usually the result of overexerting yourself in high temperatures.

Heatstroke happens when your body’s temperature exceeds 103 degrees Fahrenheit

“With heatstroke, the body tries to lower its internal temperature by systematically shutting down organs to protect the heart and brain,” cardiologist Paula Montana De La Cadena told Reader’s Digest.

If someone starts presenting signs of heatstroke, call 911. In the meantime, get them into a cool or at least shaded area as soon as possible. If you are near a home, put cool towels on their body to lower their temperature, and try to get them to drink some water.

To avoid heatstroke, the biggest thing to remember is: Stay hydrated.

Dehydration is already in place when you feel like you’re thirsty (and likely even when you don’t), so drink water consistently on hot days even when you don’t crave it.

Similarly, make sure to stay away from strenuous outdoor physical activity such as exercise or yard work. Heatstroke can happen suddenly, so it’s worth it to take extra precautions on hot days.

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