There are some parameters on what 'humid' is from an exercise physiology point of view. A body at total rest produces heat as a result of cellular metabolism. This heat can be dissipated via four different routes. Evaporation, conduction, convection and irradiation. When the air is 'humid' that evaporation route fails and body temperature can rise. This is most often the source of the deaths we see in American Football in the pre season which usually occurs in August. Take a big athlete, cover him in insulating material and run him around for an hour. The best sweat is the sweat you don't see as it reaches the surface of the skin it immediately evaporates into the air, taking along a bit of heat with it. If sweat is dripping down your face the air is most likely humid. Arnold New Jersey