For many people, summer is their favorite time of year. However, summer also brings the risk of dangerously high temperatures that can become lethal. In the U.S., hundreds of people working or playing outside – even those who seem healthy – succumb to heat-related illnesses each year.

A heat wave with high humidity will envelop large parts of the U.S. in the coming days. NPR asks University of Illinois Health's Dr. Sheetal Rao about staying safe and comfortable.