Although the rate at which water evaporates varies depending on temperature, humidity, wind speed and other factors, the average swimming pool loses about 1/4 inch of water per day. Direct sunlight also speeds the rate of outdoor water evaporation.
The rate of outdoor water evaporation differs from one geographic region to another. It tends to be slower along coastlines, where humidity is relatively high, and faster in dry climates, such as the Southwestern United States. Such regions typically receive more direct sunlight than others, which increases the rate of outdoor water evaporation. As water evaporates, it becomes an atmospheric gas or vapor, continuing the natural water cycle.