Warning signs: Weakness, dizziness, or collapse
Heat exhaustion often makes people get dizzy, feel the need to sit down, or even pass out momentarily. “Which is sort of a good thing,” says Bergeron; “that is, it stops your body from continuing before you get into more serious trouble.”
The hotter it gets outside, the more common these symptoms are. But Bergeron says it’s important to remember that, for people doing strenuous workouts, exertional heat illness can occur in relatively cool conditions, as well.