A question often asked is, "What's the effect of humidity in cold weather?" According to most books, having a higher humidity makes our body evaporate less water, resulting in less cooling. If that theory is extrapolated to very cool conditions, it would say that a cold and moist atmosphere would result in a person not being as miserable as if it were a cold, dry atmosphere. But it is not so. The reason is that people wear clothing. To an unclothed person, it is probably correct that in the humid atmosphere you would not be as cold as in the dry atmosphere. But we wear clothing. Often, as the humidity in the air increases, the insulating value of clothing decreases because of the moisture captured on the fibers of the clothing. This is the wicking effect of moisture in clothing. It can greatly accelerate the heat loss through clothing. Even though the clothes do not appear wet, the humidity in the air may create a thin layer of moisture on the fibers and result in greater conduction, or transfer, of heat through the clothing.

The person who says, "The coldest I have ever been was that cold, windy day when the humidity was so high," probably is telling the truth. It probably is realistic that it was because of the humidity reducing the insulating value of the clothing rather than the direct humidity effect on heat transfer from a person if they were unclothed.

We have introduced the energy budget of an individual, the forms of energy, and the concept that your comfort is determined not only by air temperature, but by wind, humidity, sun, thermal radiation from other sources, and by factors such as clothing, internal heat source, and evaporation. These are the factors of the energy budget. They are significant for animals and for the success and productivity of crops. We will now look more at how the specific energy budget of crops.