On hot summer days while moving in a bus the distant spot on highway appears to be wet even though It is not actually wet. What is this effect known as?

On hot summer days while moving in a bus the distant spot on highway appears to be wet even though It is not actually wet. Which physical phenomenon is responsible for this effect.

On hot summer days while moving in a bus the distant spot on highway appears to be wet even though It is not actually wet. Draw the ray diagram showing this physical phenomenon.