The weather is so hot that the ups and downs of the scenery become blurred. What is the phenomenon?

This is a very common phenomenon in nature. Due to the high temperature, the evaporation of water in ground objects and soil is intensified. When the weather is hot, under the strong sunlight, the hot airflow rises and refracts. So when the weather is particularly hot, the distant scenery will fluctuate in the air and become blurred, just like water ripples.