The higher the red line creeps up the thermometer gauge, the more red flags for outdoor exercise.
Summer temperatures shouldn’t stop you from jogging, hiking or playing sports outside – but they should alert you to the danger of heat illnesses brought on by exertion.
“Think of the heat like you think of a steep hill: Walking is good, but walking up a steep hill is much harder, so scale back the intensity and use more common sense to exercise safely,” said Dr. Clifton Callaway, a professor and executive vice chair of emergency medicine at the University of Pittsburgh.
More than 600 people die every year in the U.S. from preventable heat-related illnesses, according to the