My friends tell me that it is the humidity that causes heat-related illnesses and I say it is the temperature? Which of us is right?
You are both correct. During hot conditions the body loses its ability to radiate heat from its surface. Air temperature is a key factor in determining your risk for overheating, but the humidity level, or the water content of air, is equally important. Several football deaths have occurred with air temperatures below 75o F at 95 percent humidity levels. High humidity levels reduce the evaporation of sweat from the skin. Even though it may seem you are sweating a lot when it is humid, the sweat is mostly rolling off the skin and is not really contributing much to the cooling process. Sweat alone does not cool the body. It is the evaporation of sweat that cools the body. The combination of high air temperatures and high humidity levels increase the risk for heat illness to occur.
Stephen D. Ball, Ph.D., Associate Professor, Nutritional Sciences, College of Human Environmental Sciences, University of Missouri Extension
Last update: Thursday, December 04, 2008