“Extreme heat kills,” said  Dr. Jay Lemery, an emergency medicine physician and co-director of the Climate and Health Program at CU Anschutz Medical Campus. “It's a force multiplier for preexisting medical conditions like diabetes or COPD, asthma or coronary artery disease.” When people with these preexisting conditions are stressing themselves in the extreme heat that can put them into crisis. When they come to the emergency room, they may have shortness of breath or chest pain but not symptoms of a classic heat stroke.