When particles falling from clouds reach the surface as precipitation, they do so primarily as rain, snow, freezing rain, or sleet. Why are there different types of precipitation? It has to do with the ability of water to change phase. Where we live, precipitation usually begins falling out of a cloud as ice particles. What determines the precipitation type is the temperature between the cloud bottom and the ground.
If the temperature remains above freezing from the cloud bottom to the ground, precipitation particles melt into liquid droplets and are called rain. If the temperature underneath a cloud stays below freezing all the way to the ground, the ice crystals never melt and snow falls. Ice storms occur when precipitation particles melt and then fall through a layer of cold air near the ground. The two precipitation types most common during ice storms are freezing rain and sleet. Freezing rain forms when a thin layer of cold air near the surface causes melted precipitation to become super cold. It then freezes on contact with exposed objects on the ground whose temperature is below freezing. Sleet consists of translucent balls of ice that are frozen raindrops. It occurs when the layer of subfreezing air at the surface is deep enough for the raindrop to freeze.
When sleet hits the surface, it bounces and does not coat objects with a sheet of ice, as freezing rain does. Freezing rain covers everything in a sheet of ice, creating shimmering landscapes. However, even a little freezing rain causes treacherous road conditions and tree and power lines to snap.
