What is Humidity?
Humidity is the amount of moisture in the air. It can be measured in various ways, but the most usual is to describe it as 'relative' humidity. This is expressed as a percentage. A relative humidity of 100% means the moisture content of the air is the maximum possible at any particular temperature. The hotter the air, the more moisture it can hold.

Why is it Important?
When relative humidity is low, evaporation is rapid. Soil dries out, wet clothes dry quickly and perspiration evaporates from the skin. When relative humidity is high, clothes dry slowly and body sweat cannot evaporate easily. We feel sticky and hot and because our perspiration cannot evaporate quickly, we feel uncomfortable. We can stand dry heat much better than damp heat which makes us feel listless and takes our energy away.