There are 4 main types of precipitation: rain, sleet, snow, and hail. Rain falls in heavy drops that form from melted ice crystals in clouds. Snow falls when ice crystals remain frozen as they fall from cold clouds, joining together to form snowflakes. Sleet is partly frozen rain that forms when raindrops pass through a layer of cold air near the ground. Hail consists of balls or chunks of ice that can form in tall, dense cumulonimbus clouds.