These accumulations of ice make walking and driving extremely dangerous. A common phenomenon that occurs every so often is freezing rain. Freezing rain is a form of precipitation, and certain conditions have to be met to generate moisture from the sky, and have the moisture fall in the form of freezing rain.
Freezing rain is a specific form of precipitation, as is rain, drizzle, sleet, and hail.
It is the result of water particles falling as snow, then encountering a layer of warm air where the particles melt into rain. However, before the rain hits the ground, it goes through a cold layer of air just before the surface of the ground. The droplets are cooled, forming supercooled drops, drops that are cooled to below freezing but are not frozen. When these supercooled drops hit the ground, they thin out and freeze, instantly, forming a thin film of ice. Both types, however, can be deadly.