Rain is a term used to describe the
precipitation of
liquid water from the
solution of the
air. Generally, raindrops have diametres of approximately 0.5mm. Smaller droplets are referred to, informally, as
drizzle.
On
average, rain conists of about 100 to 1000 drops per cubic
metre. Smaller droplets are generally more numerous than larger ones; this maintains a more constant rate of water per unit time. The
cohesion of water is such that droplets of up to 4mm in size can be maintained, larger ones are unstable and short lived.
Rain is catagorized by
meteorologists in accordance with its rate of fall. Heavy rain is classified as more than 7.6mm per hour; light rain is classified as less than 2.5mm per hour.
The most rained on point on
Earth is
Mount Waialeale in
Hawaii. In the last 20 years it has received an average of 11 700 mm of rain. Areas with more than 1 500mm of rain are considered very wet, and those that receive less than 250mm are considered quite dry.
Rainfall is distributed quite unevenly over the surface of the
Earth, with
equatorial desert regions and
Antarctica receiving a very small percentage of the total and
temperate and
tropical rainforests receiving copious quantities.
Over most of Europe, South America, eastern North America, and central Africa, the annual rainfall exceeds 500 mm (20 inches), while over most of Asia, excluding India, Tibet, and China, the annual rainfall is less than 500 mm, being less than 250 mm in a long tongue extending from Arabia across to northeast Mongolia. The central regions of Australia, most of northern and a part of southwest Africa, portions of the intermontane area of the United States, and portions of the west-central coast and southern east coast of South America also have less than 250 mm of rain in the year. Portions of the western coast of Africa, between the Equator and 10° N, a strip of the western coast of India, parts of Assam, a coastal strip of Myanmar (Burma), windward mountain slopes in the temperate latitudes of North and South America, and many isolated tropical stations average more than 2,500 mm of rain in the year. Rainfall intensities greater than 30 mm in five minutes, 150 mm in one hour, or 500 mm per day are quite rare, but these intensities on occasion have been more than doubled for the respective durations.
Source: CIA Annual World Factbook
Just statistics, no copyrights, don't worry.