The National Weather Service and Centers for Disease Control and Prevention have introduced a new heat risk system that uses a five-color scale to warn Americans of dangerous heat conditions. The system combines meteorological and medical risk factors to determine the heat risk for a given location and provides a seven-day forecast. The worst category, magenta, indicates ‘rare and/or long-duration extreme heat with little to no overnight relief.’ The system is designed to help people understand the health risks associated with heat and to take precautions to avoid heat-related illnesses.