Temperatures warmer than the pavement cause moisture on the ground to freeze rapidly and attach itself to the pavement. Sudden changes in temperature–which are common after winter storms–often cause snow to melt onto roadways and create black ice.
Black ice can also form when snow or light rain falls on still-frozen concrete, turning it to ice upon contact. This quick freezing is what gives black ice its signature thin layer.
Black ice gets its name because the narrowness of the ice makes it practically invisible once it’s frozen against the pavement. This invisibility is what makes black ice one of the most dangerous surfaces for drivers.