Rain is when water falls from clouds in droplets that are bigger than 0.5 mm. Droplets of water that are about 0.2mm to 0.45mm big are called drizzle. Rain is a kind of precipitation. Precipitation is any kind of water that falls from clouds in the sky, like rain, hail, sleet and snow. It is measured by a rain gauge. Rain is part of the water cycle.
Some places have frequent rain. This makes rainforests. Some have little rain. This makes deserts.
A rainstorm is a sudden heavy fall of rain. It may cause flash floods in valleys. Heavy rain for a long time may make floods that destroy houses and drown people. Also, landslides may happen.
When the Sun heats the Earth's surface, the ground heats the air above it. Convection makes the air rise and cool. When it cools to the dew point, clouds form and rain follows.This usually occurs on flat land. This type of rainfall often causes summer showers and thunderstorms.