GRAND RAPIDS, Mich. (WOOD) — Summer heat is building this week, which will likely send many flocking to the lakeshore. There, they could glance a mirage floating above the water.

Mirages over Lake Michigan typically appear upside down and above the horizon. These are known as “superior” mirages and were given their name because they float some distance above the horizon.

Often, they can be images of ships or even the buildings of Chicago, which typically aren’t visible from our shores.

Lake Michigan mirages are most common on hot, quiet days with very little wind. The weather pattern this coming week will guarantee that type of atmosphere.

The reason is that the temperature of the air can influence its density and therefore its index of refraction. The most spectacular mirages occur when the lake water is very cold, the land temperature is very hot and an east wind carries a layer of warm air out above the still-cold air hovering over the lake’s surface.

This usually happens early in the summer, when the land heats up quickly due to the directness of the angle of the sun. The lake water takes much longer to heat up, creating a big temperature difference in air masses.

When the warm air slides out over the cold air on the lake, it forms something called an “inversion” over the water. The change in air density bends light waves and creates the mirage.

It’s not very hard to think about light waves bending. Just think of how a straw looks when you put it in a cup of water. The light cutting through the different densities of water and air makes the straw look like it is bent.

Be on the lookout for ghostly looking ships or buildings this week, and let us know if you see any sliding across the summer sky.

Photos can be emailed to ReportIt@woodtv.com. Be sure to include when and where your photo was taken, plus the name of the person who took it.