Jack Frost is a personification of frost, ice, snow, sleet, winter, and freezing cold. He is a variant of Old Man Winter who is held responsible for frosty weather, nipping the fingers and toes in such weather, coloring the foliage in autumn, and leaving fern-like patterns on cold windows in winter.
19th-century cartoon depicting Jack Frost as a United States major-general during the American Civil War
Frost on a window
Frost is a thin layer of ice on a solid surface, which forms from water vapor that deposits onto a freezing surface. Frost forms when the air contains more water vapor than it can normally hold at a specific temperature. The process is similar to the formation of dew, except it occurs below the freezing point of water typically without crossing through a liquid state.
A patch of grass showing three zones. crystalline frost in the below-freezing shade (blue, lower right) frost in the warming but still below freezing strip most recently exposed to sunlight (white, center) frost-free region: here, the previous frost has melted from a more prolonged exposure to sunlight (green, upper left.)
A spider web covered in air hoar frost
Hoar frost on the snow
Depth hoar, imaged with optical (left) and scanning electron (right) microscopy
