When I think about mirages, I think of two things: Vegas and the scorching hot desert (I guess that's one thing?). I never think about the cold, though. Hell, I never even knew mirages happened in the cold!
This picture, with the car floating in the air, proves me wrong. It was taken in February in Canada when the temperature was -10°F. A mirage effect in the cold works essentially the same as it does in the heat.
New Scientist explains:
The black asphalt of the road surface has been heated just a few degrees above the ambient temperature and as a result, a thin layer of air above the road surface warms up. The layer of warm air has a lower refraction index than the denser, colder air above it. The difference between them creates a boundary which behaves as a mirror, reflecting distant objects, in this case the blue winter sky, which makes it looks as if the car is floating above the road's surface.