Heat Index Hot conditions put your body under a lot of stress.
Physical activity stresses the body even more.
When heat is combined with physical activity, loss of fluids, fatigue, and other conditions can lead to a number of heat-related illnesses and injuries. Death is even possible. Heat stress is commonly associated with warm weather. It is true that warm weather increases the number of heat-stress injuries and illnesses. Warm weather is not the only cause of heat stress, though.