World is an amazing place. Each and every occurrence has its cause that is far more complex that it may seem on the first glance. Even such mundane phenomenon as rain is a fascinating mixture of physics and chemistry. Do you know where does the rain comes from? How does rain fall? Or does the raindrops always have to be made out of water? We’ll answers all those questions in this article, so prepare for a dose of new weather-related knowledge!


What is the definition of rain?

The definition of rain is as follows: rain is a condensed moisture (created out of water vapor) falling to the ground in form of droplets. When the moisture accumulates in form of clouds, it gradually becomes heavier and heavier, which subsequently results in it falling down due to the force of gravity. Precipitation is an important step in the water cycle, during which vapor is turned back into liquid state and returned to the earth.

Intensity of a rain is measured with a tool called rain gauge, which collects rainwater in order to determine its amount. Depending on its intensity, the rainfall can be classified into one of following types:


  • Light rain, during which the rainfall rate is lesser than 2.5 mm/h (around 0.1 in/h)
  • Moderate rain, when the rate is between 2.5 mm/h (around 0.1 in/h) to 7.6 mm (0.30 in/h)
  • Heavy rain, with rate of less than 7.6 mm/h (0.30 in/h) to around 50 mm/h (2.0 in/h)
  • Violent rain — when the precipitation rate is bigger than 50 mm/h (2.0 in/h)


Although on our planet water is the main substance to be a part of the rain, theoretically every substance with the liquid state could potentially produce a rain. It is proven that in the other parts of the Universe it is possible to encounter rain composed of methane (Titan), sulfuric acid (Venus) or even iron (OGLE-TR-56b).