Rainfall Patterns: how much is too much rain?

Rainfall is called precipitation. Rain is freshwater, not saltwater.

Precipitation includes rain, drizzle, sleet, snow, graupel, and hail. It is water vapour that condenses and falls to earth. (Mist and fog are not precipitation because they do not fall; the moisture remains in a cloud near the ground).

A little bit of very small drops of rain that falls very gently is called drizzle.

A little bit of rain that falls steadily is called a rain shower.

Rain with small ice pellets is called sleet.

Rain with heavy and large ice pellets is called hail.



Snow with a crust of ice is soft hail, or graupel.

Snow is flakes of moisture.

Most rain occurs in tropical areas. This includes tropical rain forests. There are other rain forests in cold regions.

In the tropics, there are usually two seasons: the wet season (the rainy season) and the dry season. [In temperate zones, there are four seasons: summer, autumn, winter, spring.]

Rain is measured in millimetres and centimetres (or inches) in a special rain gauge (usually a glass or plastic tube).

Over the land, all over the Earth, the average annual (yearly) rainfall is 71 centimetres (28 inches). Over the sea, the average annual rainfall is 127 centimetres (50 inches). Therefore, there is more rain over the sea than over the land.  Together, over all of the globe – sea and land – the average annual rainfall is 98 centimetres (39 inches).

So, too much rain is just the amount of rain above the annual rainfall for each specific location.

For example, a rain forest has a minimum annual rainfall of 180 centimetres (71 inches) in a range from 175-201 centimetres (69-79 inches). Too much rainfall in a rain forest would be more than 201 centimetres (79 inches) in one year, or too much per month compared with the average monthly rainfall.

Mountain locations, near the equator, are the wettest – the rainiest – places on Earth. Deserts are the driest places on Earth, with very little annual rainfall.

Sumatran Tiger








Photographer: Martina Nicolls


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