Mixed precipitation

Rain and snow mixed or sleet is precipitation composed of rain and partially melted snow. Unlike ice pellets, which are hard, and freezing rain, which is fluid until striking an object, this precipitation is soft and translucent, but it contains some traces of ice crystals, from partially fused snowflakes. In any one location, it usually occurs briefly as a transition phase from rain to snow or vice versa. Its METAR code is RASN.

This precipitation type is commonly known as sleet in most Commonwealth countries, including Canada. However, the United States National Weather Service uses the term sleet to refer to ice pellets.

This precipitation occurs when the temperature in the lowest part of the atmosphere is slightly above the freezing point of water (0 °C or 32 °F). The depth of low-level warm air (below the freezing level) needed to melt snow falling from above to rain varies from about 230–460 m (750–1,500 ft) and depends on the mass of the flakes and the lapse rate of the melting layer. Rain and snow typically mix when the melting layer depth falls between these values.

Wintry showers is a somewhat informal meteorological term, used primarily in the United Kingdom, to refer to various mixtures of rain, graupel and snow. Though no "official" criteria exist for the term, in the United Kingdom the term is not used when any significant accumulation of snow on the ground takes place. It is often used when the temperature of the ground surface is above 0 °C (32 °F), preventing accumulation from occurring even if the air temperature is marginally below 0 °C (32 °F); but even then, the falling precipitation must generally be something other than exclusively snow.

...
Wikipedia