Frozen dew is a type of precipitation that forms when the temperature drops below freezing. It is composed of tiny ice crystals and is also known as HOAR, RIME, or FROST. HOAR is a white deposit of frozen water vapor that forms on surfaces exposed to the air. RIME is a white deposit of frozen water droplets that form on cold surfaces. FROST is a thin layer of ice that forms on cold surfaces when the temperature drops below freezing.