Evaporation is simply the process of conversion of liquid water into vapor. Evaporation is a continuous process that occurs constantly outdoors in the lakes and ponds and is the reason why it rains. Evaporation is caused by the absorbance of heat from a source that will allow the conversion from a liquid to a vapor escaping a body of water.As pool water evaporates, it cools the pool water and the air in the pool room. Learn more about evaporation, condensation and dew point in our blog How 3 Key Dehumidification Terms Relate.