Frost

Frost, frozen atmospheric moisture formed on objects whose surface temperature is below 32°F (0°C), the freezing point of water. Hoarfrost forms in roughly the same way as dew, but owing to the low temperature, the water vapor sublimes from gaseous to solid state to form ice crystals on the surface. The delicate patterns often seen on windows are hoarfrost. Glazed frost usually forms when rain falls on an object below freezing; it can be seen, for example, on telegraph wires. Rime occurs when supercooled water droplets contact a surface that is also below 32°F; it may result from fog or drizzle. The first frost of the year signifies the end of the growing season.