Muscle cramping is a sign of dehydration. Dizziness and confusion are signs of heat exhaustion. The rate of sweating is higher with increased humidity, but the cooling effect is less. Heat cramps are the least severe and usually occur in the arms, legs and abdomen. Heat exhaustion is due to more profound water and electrolyte loss.
Heat stroke is life threatening and requires immediate medical attention.
High body temperature and sever water loss occur. Many victims stop sweating. Damage to internal organs may occur. Get the person out of the sun and rub skin with bags of ice. Light colored clothing reflects light and heat, so wear these types of things on hot days.