What can happen if you get too dehydrated or exert yourself in the heat too long? Here are some possibilities, from the least to the most severe:
Heat cramps ― muscle pain or spasms
Heat exhaustion ― a state of elevated body temperature that's a precursor to heatstroke
Heatstroke ― a life-threatening condition in which your body temperature rises above 106˚ F
If you experience muscle cramping, dizziness, fast and shallow breathing, cold and clammy skin, or nausea or vomiting, get out of the heat immediately and get some water. Heat-related illnesses are no joke, so don't take any chances!