From where does rain come?

Explanation

A cloud is a visible mass of liquid droplets or frozen crystals in the atmosphere above the surface of Earth. Clouds are formed when invisible water damp condendes to small visible droplets or crystals. Clouds are actually heavy. The water in an average cloud can weigh several million tonnes - but of course it is rather big also. When it rains the sky often turns grey, but above the clouds the sky is always blue.