Black ice is when moisture on the road quickly freezes to ice, causing treacherous slipperiness.

The risk of black ice is greatest when the weather clears up after rain or fog and the temperature is around 0 °C. However, since road surface temperatures are usually much colder than the ambient temperature, you should expect roads to be slippery as soon as the thermometer shows +4 °C or colder.

Black ice is most common in winter but can also occur on cold days in spring and autumn as well.

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