Complications of heat exhaustion include nausea, vomiting, dehydration and muscle weakness. If the activity is not stopped and the person left in a hot environment, there can be progression of symptoms to heat stroke, a life threatening emergency.

Heat stroke is a medical emergency and can be fatal if not promptly and properly treated. The cause of heat stroke is an elevation in body temperature, often accompanied by dehydration. Heat stroke is diagnosed by observation of the symptoms and signs in a person exposed to extreme temperatures.

Heat exhaustion is usually accompanied by a fever no higher than 104 degrees , excessive thirst, nausea, fainting, cool and clammy skin, weakness, muscle aches, heavy sweating, slow heartbeat and dizziness. Heatstroke may develop following heat exhaustion if the condition is not treated.