Precipitation

Sometimes water droplets (or ice crystals) in a cloud join together and grow larger. If they grow too large to be held up in the atmosphere, they fall down. Whenever water falls from the sky to the surface of the earth, this is called precipitation. Rain, snow and hail are types of precipitation.

Rainfall is measured in millimeters over a period of time such as a day. Rainfall is measured using an instrument called a rain gauge. Look at the picture below.