This document summarizes the four most common heat-related illnesses (HRIs): heat rash, heat cramps, heat exhaustion, and heat stroke. It describes the signs and symptoms of each illness and the appropriate first aid responses. Heat rash causes itchy red bumps that need to be kept dry. Heat cramps result in painful leg or stomach muscles and require drinking water or sports drinks. Heat exhaustion may cause headache, dizziness, and nausea, requiring rest in shade with cold compresses. Heat stroke is the most severe with high fever and potential for seizures, requiring immediate emergency medical care.