Image Courtesy of Kimberly Comstock/University of Washington
Drizzle is light precipitation that is made up of liquid water drops that are smaller than rain drops. Drizzle can be so light that only a millimeter of water falls to the Earth’s surface in one day. It is produced by stratocumulus or stratus clouds.
The water drops that make up drizzle are small (a drop of drizzle has the same thickness as human hair) and because of their small size much of the drizzle evaporates before falling to the ground. Drizzle lowers visibility so it is harder to see objects in the distance when it is drizzling than on a clear day.
Drizzle commonly occurs over the ocean, where it has an effect on the thickness of clouds. It also influences how much those clouds reflect sunlight away from the surface of the Earth.
source: windows to the universe