SLEET

'Sleet' is a term used in a variety of ways to describe precipitation intermediate between rain and snow but distinct from hail.

Contents

In the UK and Commonwealth countries

In the United States

References

In the UK and Commonwealth countries

In British English and in many Commonwealth countries sleet refers to snow that has partially melted on its fall to the ground due to surrounding air that is sufficiently warm to partially melt it while falling but not warm enough to fully melt it into rain.^[1] Thus it refers to partially melted droplets, a mixture of snow and rain. It does not tend to form a layer on the ground, unless the ground has a temperature that is below freezing, when it can form a dangerous layer invisible on surfaces known as black ice (though black ice may also develop when rain freezes upon contact with the ground, known as freezing rain).
The METAR code for this usage is 'SNRA' or 'RASN' depending on how much melting has occurred.

In the United States

In American usage, sleet is a form of precipitation consisting of frozen raindrops or refrozen partially melted snowflakes, also known as 'ice pellets'.^[2] This is often mistaken for hail, but forms in a different fashion and the individual ice pellets in sleet are usually (but not always) smaller than typical hailstones.^[3] Sleet may bounce when it hits the ground, but generally does not freeze into a solid mass unless mixed with freezing rain.
The METAR code for ice pellets is 'PL'.

References

1. Water in the atmosphere
2. Sleet (glossary entry)
3. Hail (glossary entry)