How Light Bends To Create A Mirage

I remember as a young child, riding in the car on the rural roads of Louisiana and in the distance, the roads appeared wet. Only to see "the water" vanish as we approached. That phenomenon always puzzled me, and it wasn’t until years later that I had my answer: a mirage.

In weather terms, a mirage is an optical illusion caused by the bending of light as it travels through layers of air with different temperatures. When air near the ground is much warmer or colder than the air above it, light rays curve instead of traveling in a straight line, creating distorted or displaced images of distant objects.

The most common type of mirage is the inferior mirage, often seen on hot roads or deserts, where the surface heats the air just above it. That warm air is less dense than the cooler air above, causing light from the sky to bend upward toward the eye. The result can look like shimmering water on pavement or reflections that seem to vanish as you approach. Despite appearances, there’s no moisture on the road, just refracted light.

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Mirages can also occur in cold weather. Superior mirages form when a layer of cold, dense air sits near the surface with warmer air above it, a setup known as a temperature inversion. In these cases, distant objects such as ships, coastlines or buildings can appear stretched, stacked or even floating above the horizon. These cold-weather mirages are often seen over icy lakes, oceans or snow-covered terrain.

So take notice next time you see this phenomenon on a hot day, it’s not just your eyes playing tricks on you, it’s the weather around you putting on a show!

Jennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.