The water cycle involves evaporation of water from bodies of water by heat from the sun, condensation of water vapor into liquid water clouds, precipitation of water back to the Earth as rain, snow, sleet or hail, and run-off of water over the ground or absorption into the ground. Key steps in the water cycle include evaporation of water into vapor, condensation of vapor into liquid water clouds, precipitation of water back to Earth, and run-off of leftover water over or into the ground.