The various types of precipitation—rain, snow, sleet, hail, etc.—have one important thing in common: water. Here is how these different types form. Sleet is a form of wintry precipitation, but its exact definition depends on location. In some countries — for example, the United Kingdom, Canada and Australia — the term refers to snow that has partially melted on its way to the ground. Sleet is type of precipitation distinct from snow, hail, and freezing rain. It forms under certain weather conditions, when a temperature inversion causes snow to melt, then refreeze. Sleet occurs when snowflakes only partially melt when they fall through a shallow layer of warm air. These slushy drops refreeze as they next fall through a deep layer of freezing air above the surface, and eventually reach the ground as frozen rain drops that bounce on impact.
