Rainwater is technically distilled because it is created by natural distillation. Water evaporates from the sun's heat and rises into the sky, where it cools and condenses, generating small water droplets that form clouds. These clouds eventually release the water in the form of rain. Rainwater will come into contact with various airborne pollutants on its approach to the ground, which means it will not be as clean as artificial distilled water once it reaches the ground.