An updated free app — redesigned by the Center for Disease Control and Prevention’s (CDC) National Institute for Occupational Safety and Health (NIOSH), along with the U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA) — can help construction workers stay safe when working outdoors in hot weather. The OSHA-NIOSH Heat Safety Tool mobile app, for iOS and Android devices, determines heat index values — a measure for how hot it feels — based on temperature and humidity. An updated version of OSHA’s original Heat Safety Tool, the app uses the device’s geolocation capabilities to pull temperature and humidity data from National Oceanic and Atmospheric Administration satellites to determine the heat index. The app shows the current risk level (minimal, low, moderate, high or extreme) and forecasts the hourly heat index throughout the entire workday giving employers information they can use to adjust the work environment as needed to protect workers. Construction workers exposed to hot and humid conditions are encouraged to use the app to check weather conditions if they will be outdoors for short or long periods during the summer heat.