The temperature in the cave changes little in winter and summer. Because of its good thermal insulation performance, it is warm in winter and cool in summer. The cave was dug on the hillside, so its "roof" and "wall" are quite thick. When people dig caves, they choose places with hard soil. This thick and hard "wall" is not easy to transfer heat. Therefore, the top and wall of the cave can neither directly absorb heat from the atmosphere nor directly dissipate heat to the atmosphere, only the hole is in direct contact with the outside world. Therefore, the temperature change in the cave always lags behind the external temperature change, and the temperature difference changes little.