High temperatures along with high humidity also increase maintenance requirements. With each 1-degree increase in body temperatures above normal, the metabolic rate increases about four percent. Wool serves as a protectant from heat, particularly against solar radiation. Body coat both reflects and radiates heat from the fiber tips and insulates the body surface. For example, temperatures of up to 150F at the fleece tip of full-fleeced sheep have been measured without showing an increase in the temperature at skin surface.
Humidity levels exert a greater effect on energy requirements than do absolute ambient temperatures.
The higher the humidity level at a given temperature, the harder it becomes for animals to dissipate body heat. This extra effort in turn increases the energy required to maintain normal bodily functions. Fatter sheep are more susceptible to high environmental temperature and humidity stress than those in normal body condition. A nutrient deficiency during snowstorms is usually associated with cold temperatures and is often complicated by high wind velocity and wet fleeces. Again, the most critical nutrient that is required in this situation is energy.