Why is the winter climate in Chongqing so cold?

Chongqing is located in Sichuan Basin, with Yunnan-Guizhou Plateau in the south, Hengduan Mountains in the west, Qinling Mountains in the north and Xuefeng Mountain in the east. The key is that Chongqing is surrounded, which is good. The temperature is not low in winter, because the cold air from the north to the south is blocked by the surrounding mountains, but because the terrain is closed and the water vapor is not easy to spread out, it is gloomy. As for the cold, Chongqing is not as cold as Hangzhou at the same latitude, and it is warm in winter.