Sleet is a distinct type of winter precipitation, often confused with other forms of frozen precipitation. It represents a specific atmospheric phenomenon with unique characteristics that differentiate it from rain, snow, or freezing rain.
What Sleet Is
Sleet consists of small, translucent ice pellets that fall to the ground. These pellets are typically globular in shape, and their diameter usually ranges from 0.1 to 0.5 inches (2.5 to 13 mm). Upon impact with hard surfaces, sleet often bounces, producing a distinct sound. This form of precipitation is also commonly known as ice pellets, which is the official term used by the U.S. National Weather Service.
Sleet is distinct from snow or freezing rain because it arrives at the surface as already frozen solid particles. Unlike snow, which is delicate ice crystals, sleet is essentially frozen raindrops. Its solid, pellet-like form distinguishes it from the smooth ice layer of freezing rain.
The Formation of Sleet
Sleet formation requires a specific atmospheric temperature profile. Precipitation begins as snow in a cold layer high in the atmosphere. As snowflakes descend, they encounter a warmer layer where temperatures are above freezing, melting them into raindrops.
These liquid raindrops then pass through a deep layer of sub-freezing air near the ground. This cold layer causes the raindrops to refreeze into small ice pellets before reaching the surface.
Distinguishing Sleet from Other Precipitation
Sleet differs from other winter precipitation types due to distinct formation processes. Snow consists of ice crystals that remain frozen from clouds to the ground, requiring below-freezing temperatures throughout the atmospheric column. Sleet, however, involves snow melting into rain in a warm layer, then refreezing into ice pellets in a deep cold layer near the surface.
Freezing rain also involves a warm layer, but the cold layer near the ground is much shallower. Liquid rain falls through this shallow freezing layer without enough time to fully refreeze. Instead, it becomes supercooled liquid that freezes upon contact with surfaces at or below freezing, forming a glaze of ice. Rain occurs when temperatures remain above freezing throughout the entire descent of water droplets.
Experiencing Sleet Weather
When sleet falls, the small ice pellets produce a distinctive “tinkling” or “rattling” sound as they strike hard surfaces like windows, roofs, and car windshields. This audible characteristic helps distinguish sleet from soft snow or silent freezing rain. The pellets feel hard and icy upon impact, different from the soft texture of snowflakes.
Sleet does not accumulate as deeply as snow, but it can form a slick, crunchy, or hazardous layer on surfaces. The accumulation of these ice pellets can make roads and sidewalks slippery, reducing traction for pedestrians and vehicles. While not forming a smooth glaze like freezing rain, the hard pellets create a treacherous texture.