The four common types of precipitation include rain, snow, hail and sleet. Precipitation occurs when water vapor forms in the atmosphere, condenses and falls to the ground.
Rain occurs when water vapor condenses around dust particles inside clouds. This forms water droplets that, when too heavy for the cloud to hold, fall to the ground as rain. If the droplets freeze before they reach the ground, the water becomes sleet or ice pellets.
Unlike sleet, hail forms in storm clouds when upward drafts prevent the water droplets from falling until the droplets form hailstones. Hail grows as it collects more water droplets. The hailstones fall to the ground in ice roughly the size of small rocks, but the size may vary. Snow is also ice, but snow forms when water vapor turns into ice crystals, skipping the liquid phase.