Drizzle is a light rain precipitation consisting of liquid water drops smaller than those of rain, and generally smaller than 0.5 mm (0.02 in) in diameter. Drizzle is normally produced by low stratiform clouds and stratocumulus clouds. Precipitation rates due to drizzle are on the order of a millimetre per day or less at the ground. Owing to the small size of drizzle drops, under many circumstances drizzle largely evaporates before reaching the surface, and so may be undetected by observers on the ground. The METAR code for drizzle is DZ.
While most drizzle has only a minor immediate impact upon humans, freezing drizzle can lead to treacherous conditions. Freezing drizzle occurs when supercooled drizzle drops land on a surface whose temperature is below freezing. These drops immediately freeze upon impact leading to the buildup of sheet ice on the surface of roads, and very heavy accumulations of ice on power lines, both of which have major impacts.