Precipitation Types

Regardless of cause, weather around the world falls into three basic categories; precipitation, obscurations and 'other' phenomena. Precipitation is any form of water particle, whether liquid or solid, that falls from the atmosphere and reaches the ground. The different types of precipitation are:

Rain

Most commonly observed, drops larger than drizzle (0.02 inch / 0.5 mm or more) are considered rain. However, smaller drops are also considered raindrops if, in contrast to drizzle, they are widely separated.

Drizzle

Fairly uniform precipitation composed exclusively of fine drops very close together.

Drizzle appears to float while following air currents, but unlike fog droplets, it falls to the ground.

Quite often fog and drizzle occur together.

Ice Pellets
(Sleet)

Precipitation of transparent or translucent pellets of ice, which are round or irregular hard grains of ice consisting of frozen raindrops, or largely melted then refrozen snowflakes.

Hail

Precipitation in the form of small balls or other pieces of ice falling separately or frozen together in irregular lumps.

Associated with thunderstorms, individual hail stones are ¼ inch (5 mm) or greater in diameter.

Hail sizes of 1 inch (2.5 cm) or more are indicative of severe thunderstorms.

Small Hail
(Snow Pellets)

Precipitation of white, opaque grains of ice that are round or sometimes conical. Diameters are less than ¼ inch (5 mm).

Snow

Precipitation of snow crystals that are mostly branched and in the form of six-pointed stars.

 Snow

Snow Grains

Precipitation of very small, white, and opaque grains of ice.

Basically, this is frozen drizzle.

Ice Crystals

Generally occurring in very cold regions, they are falling crystals of ice in the form of needles, columns, or plates.

Also called 'diamond dust', ice crystals appear like fog with individual water particles forming directly as ice.

The shape of the individual ice crystals causes the 'light pillar' optical effect above the light source.

Next: Obscurations