You should specifically look out for black ice:

Question

Black ice is a thin layer of ice that is clear enough for the road surface to be seen through it. Be alert to black ice any time the temperature is below freezing and the road surface looks wet.

Accepted Answer

When the temperature is below freezing and the road looks wet.

Answer

When it is snowing.

Answer

When the temperature is above freezing and there is snow on the ground.