Dehydration is a condition that occurs when the body cannot cool itself.
Heat exhaustion is a life-threatening condition that includes symptoms, such as uncoordinated walking, headache, dizziness, vomiting, and elevated body temperature.
Hypothermia is a potentially life-threatening condition that results when the metabolic heat cannot compensate for the heat loss to the environment.
Frostbite occurs when the water within body tissues crystallizes, so the body tissues become damaged.
Heat cramp is a painful, brief muscle cramp that results from exercising in a hot environment.
Let me know if it's wrong, because then that means the first two answers must be switched.
