The water cycle has no starting point. It begins in the oceans. The sun, which drives the water cycle, heats water in the oceans. Some of it evaporates as vapor into the air. This invisible vapor rises into the atmosphere, where the air is colder, and condenses into clouds. Air currents move these clouds all around the earth. Water drops form in clouds, and the drops then return to the ocean or land as precipitation as snow.The snow eventually melts back into a liquid and runs off into a lake or river, which flows back into the ocean, where it starts the process again.