Wet bulb globe temperature (WBGT) is a measurement of heat stress in a direct sunlight. This includes a number of factors: ambient temperature, wind speed, humidity, sun angle, cloud cover, solar radiation. f you work or exercise in direct sunlight, this is a good measure to monitor. The American College of Sports Medicine set down the basic guideline that any temperature where WBGT value is over 82°F (28°C) is not appropriate for competitions and sport practice.