Freezing rain is the name given to rain that falls when surface temperatures are below freezing. Unlike rain and snow mixed, ice pellets, or hail, freezing rain is made entirely of liquid droplets. The raindrops become supercooled while passing through a sub-freezing layer of air many hundreds of feet above the surface, and then freeze upon impact with any object they encounter.
The resulting ice, called glaze, can accumulate to a thickness of several centimeters. The METAR code for freezing rain is FZRA.