Wet Bulb Globe Temperature as a Measure of Vulnerability to Heat Impacts for Active Individuals

National Weather Service meteorologists rely heavily upon parameters such as heat index (HI) for determining the necessity of heat advisories and warnings. HI has been found to be an effective means of assessing heat impacts on sedentary populations, but may not fully capture the risks for active individuals. The Wet Bulb Globe Temperature (WBGT) is a composite parameter that estimates the combined effects of temperature, humidity, wind, and solar radiation on humans, and has been found to be a more effective means of assessing exertional heat illness (EHI).

The military has used the WBGT for over half a century to assess vulnerability to heat-related illness during training exercises, and experienced a resultant profound reduction in EHI during said exercises. Other organizations such as the Occupational Safety and Health Administration (OSHA) and various athletic associations also utilize the WBGT for establishing guidelines that dictate modifications in activities and work practices in given ranges of WBGTs.

This study, a partnership between the National Weather Service, Minnesota Department of Health, and the University of Minnesota, attempts to correlate daily calculated WBGT values from 1997 to 2014 for the Twin Cities metropolitan area with hospitalization data of heat-related admissions (morbidity), to demonstrate the utility of the WBGT. An analysis and theory will be provided as to how utilization of WBGT in the forecast process would enhance National Weather Service messaging of heat impacts for active persons.