ROCKFORD, Ill. (WTVO) — As it gets hotter out, drivers might be confused to see what looks like water reflecting on the road only for it to disappear when they get closer.

They might be wondering why they can see the sky on the road when it is bone dry.

As it turns out, these reflections are simply a mirage, the same kind that can be found in deserts, according to Science ABC.

Light travels at speed of around 186,411 miles per second. The speed is influenced by what it travels through, slowing when it goes from a thinner to a denser medium.

The reflective surface of something depends on its temperature. The hotter something is, the less dense it becomes.

Since roads are generally black, they absorb heat and become hotter than light-colored objects. When this happens, the air temperature just above the road becomes hotter.

When the sun’s rays reach the warmer and less dense layer just above the road, they change course due to their speed increasing. This leads to the rays being refracted into the eyes of the observer.

Because of this, drivers are seeing a reflection of the sky.

When this phenomenon happens in the desert, it can be cruel for the people that witness it. Since the reflection looks like water at first, thirsty travelers might think that they have hit the jackpot. However, as they get closer, that water disappears to just leave more sand in its wake.