Ambient air temperatures. The rate of body heat loss is inversely proportional to the temperature of the surrounding air. As temperatures decrease, heat loss increases. Air temperatures do not have to be below the freezing point of water to cause cold injuries. Prolonged exposure to temperatures as high as the 50 degree F. range can cause injury depending on other environmental factors and the degree of personal protection.
Cold injury is due, in part, to the effect of low temperatures on moisture in or on the body.
The higher the moisture content, especially on the skin surface, the more rapid the heat loss. As humidity rises, the temperature at which cold injury can occur also rises. High humidity can also induce sweating which will further reduce body heat. Heat loss is further influenced by wind velocity when humidity is high. Consult Table 9-8 for wind chill equivalent temperatures.