“No sweat” means “ it’s good,” right? Not always the case--when exercising in hot, humid weather, it means danger. Sweating can be a social problem, but it is a life-saving process for you on the track.
The core temperature of your body is maintained in a narrow range (about 97℉ - 100℉) in a wide variety of environments. This is necessary because at too low a temperature, bodily functions slow down and cease. At too high temperatures, the body essentially cooks.