(Sometimes popularly called mist. ) Very small, numerous, and uniformly distributed water drops that may appear to float while following air currents. Unlike fog droplets, drizzle falls to the ground. It usually falls from low stratus clouds and is frequently accompanied by low visibility and fog. In weather observations, drizzle is classified as 1) light, the rate of fall being from a trace to 0. 3 mm (0. 01 in. ) per hour; 2) moderate, the rate of fall being from 0. 3 to 0. 5 mm (0. 01–0. 02 in. ) per hour, and 3) heavy, the rate of fall being greater than 0. 5 mm (0. 02 in. ) per hour. When precipitation equals or exceeds 1 mm (0. 04 in. ) per hour, all or part of the precipitation is usually rain. However, true drizzle falling as heavily as 1. 3 mm (0. 05 in. ) per hour has been observed. By convention, drizzle drops are taken to be less than 0. 5 mm (0. 02 in. ) in diameter. Larger drops are considered raindrops. Compare mist.