Slight frosts
Ground frost refers to the various coverings of ice produced by the direct deposition of water vapor on objects and trees, whose surfaces have a temperature below the freezing point of water (0 °C, 32 °F)
The three main types of ground frost are radiation frost (hoar frost), advection frost (advection hoar frost) and evaporation frost. The latter is a rare type which occurs when surface moisture evaporates into drier air causing its temperature at the surface to fall at or under the freezing point of water. Rime (both soft and hard) is technically not a type of ground frost.