About Solid Precipitation |
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Solid precipitation originates in clouds where air temperatures are below freezing (0˚C, 32˚F), and generally where ground temperatures are less than 5˚C (41˚F). Solid precipitation has a variety of forms including snow, snow grains, snow pellets, diamond dust, hail, and ice pellets:
- Snow is an aggregate of ice crystals. See also About Snow.
- Ice Crystal Precipitation is made up of small ice crystals that float with the wind and fall very slowly. It is also called "diamond dust".
- Snow grains: Precipitation of very small opaque white particles of ice which fall from a cloud and which are fairly flat or elongated with diameters generally less than 1 mm.
- Snow Pellets: Precipitation of white and opaque ice particles, which falls from a cloud. These particles are generally conical or rounded. Their diameter may attain 5 mm. The term "graupel" is also used.
- Hail: Precipitation of either transparent, or partly or completely opaque particles of ice (hailstones), usually spheroidal, conical or irregular in form and of diameter very generally between 5 and 50 mm, which falls from a cloud either separately or agglomerated into irregular lumps.
The WMO intercomparisons of methods of measuring solid precipitation have focussed on falling snow and did not include hail.
![](/about/images/snowflakes.png)
Image from the Bentley Collection, Space Science and Engineering Center, University of Wisconsin-Madison
![](/about/images/frozenprecip.jpg)
Forms of frozen precipitation. Left to right: hail, graupel, sleet, snow. (From the NOAA National Severe Storms Laboratory)