Problem. A long standing problem is the ability to stay cool in hot weather, with a serious danger being heat strokes that can, at times, lead to fatality. It has long been scientifically proven and demonstrated that when hot, low relative humidity, outside air is drawn through a wetted material, the hot air will evaporate at least some of the water in the wetted material. The loss of heat energy to evaporate water in the wetter material causes the air leaving the material to have a lower temperature and a higher relative humidity. The leaving air temperature approaches the adiabatic wet bulb temperature of the incoming hot dry air, and relative humidity of the leaving air approaches 100% saturation. However, effective use of this well-known concept by a cooling vest to maintain a safe temperature in hot weather has not been realized by the conventional art.