Dangerously high heat levels forced at least one metro Atlanta school district to pull students inside Monday as heat index values head toward triple digits this week. 

Georgia Tech biology adjunct professor Mike Sawka explained that extreme heat creates severe cardiovascular strain during exercise. "The main problem with heat stress is it puts stress on the cardiovascular system," Sawka said. "The blood flow that would normally go to the muscles has to be shared by the skin. So as you exercise, you're cheating the blood flow from the heart called your cardiac output". 

Sawka noted that extended exertion in hot weather puts the human body into overdrive, triggering a progression of severe health risks. "That can lead to either heat exhaustion, heat injury, or heat stroke, which is a continuum of serious heat illnesses, with heat stroke being the most severe," Sawka said.