hoarfrost

A deposit of crystalline ice, of highly variable morphology, generally in the form of scales, needles, feathers, or fans, that forms on the vegetation cover and objects located at ground level, after the temperature drops below 0°C during the course of the night. The formation of this hydrometeor, also known as white frost, is mainly due to the sublimation of water vapor from the air on coming into contact with the cold surfaces on which it accumulates, although part of the ice can originate from the freezing of dew drops (white dew). Depending on the humidity and temperature conditions, one or the other ice-generating mechanism dominates. The word escarcha derives from the Latin term excrepitare, meaning to crackle or crack, in reference to the characteristic sound produced by the breaking of ice into pieces, similar to that of glass.