When the tiny drops of water rub and bump against each other they produce electricity. The hot air produced by lightening expands to full capacity causing thunder to occur. Precipitation is a cooling of the air that causes moisture to fall to the earth in different forms. A. Rain forms inside rain-clouds. The water vapor that evaporates from below forms tiny water droplets.
Tiny droplets form together creating bigger and heavier drops.
Once they become so heavy that the air can no longer hold them up they fall. B. Snow crystals form when water freezes inside the cloud. When the snow crystal forms together they form snowflakes. Snow falls because the amount of frozen water in the clouds becomes too heavy for the clouds to hold. Sleet is snow that melts and refreezes before it hits the ground.