Understanding the Weather: Feb. 6, 2008
Drizzle: Liquid precipitation composed of very small water droplets (0.001 to 0.020 inch in diameter) that appear almost to float while following air currents. Unlike fog, drizzle falls to the ground. It is erroneous to refer to very light rain as drizzle.
Drizzle, fog, mist: All three are composed of tiny water droplets that appear to float in the air. Drizzle droplets are large enough so that they do fall, and therefore drizzle is precipitation. Fog and mist droplets are smaller and do not fall and are not precipitation.
Fog: A visible aggregate of water droplets suspended in the air at ground level. Fog is literally a cloud on the ground. Fog droplets are so tiny that they do not fall through the air, and fog is therefore not considered to be precipitation.
Freezing rain: Rain that falls into a shallow layer of subfreezing air at the ground (usually only several hundred feet deep) and freezes upon impact to form a coating of glaze on exposed objects.
Rain:Liquid precipitation in the form of water drops with diameters greater than 0.020 inch. Drizzle, the only other form of liquid precipitation, consists of droplets 0.020 inch in diameter or smaller.
Sleet: Precipitation in the form of small ice pellets. Sleet forms when raindrops (or largely melted snowflakes), originating in warmer air aloft, fall through a layer of subfreezing air at ground level and then freeze on their way down. Sleet is often referred to as ice pellets in weather observations.