According to the National Weather Service, a WetBulb Globe Temperature (WBGT) is a measure of the heat stress in direct sunlight, which takes into account: temperature, humidity, wind speed, sun angle, and cloud cover (solar radiation). This differs from the heat index, which takes into consideration temperature and humidity and is calculated for shady areas.
Using a WBGT monitor on-site provides more accurate data than that from the National Weather Service and can help athletic programs to dictate modifications in activity (work/rest ratios, hydration breaks, equipment work, length of practice) that make sports safer for all participants. For more information: https://ksi.uconn.edu/prevention/wet-bulb-globe-temperature-monitoring/#
Step-by-Step process of using your Kestrel 5400 Heat Stress Tracker