Dehumidifiers take advantage of the phenomenon of condensation. Condensation occurs whenever a cold surface comes into contact with warmer, humid air. Some of the moisture in the air reverts to its liquid state and collects on the cold surface.
Since the coil must be colder than the air around it for the condensation to occur, the dehumidifier will ice over at surprisingly high temperatures. EnergyStar states that most residential dehumidifiers will begin to ice over if the ambient temperature drops below 65 degrees Fahrenheit.
