To start, a cloud must be formed in the atmosphere by warmer air at the surface rising in to cooler air aloft.
The water vapor in the air is condensed onto tiny pieces of dust and collected together to create the cloud.
Inside the cloud, swirling winds blow water droplets around. When the water droplets bump into each other, they join together.
Eventually, the droplets become heavy enough and start to fall.
As they fall to the surface, the droplets gather more moisture to form even larger raindrops.
Small raindrops are almost spherical or round in shape. Larger drops are flattened at the bottom, resembling a hamburger roll.