Why is Chengdu always cloudy?

Surrounded by mountains on all sides, Qinling Mountains in the north, Liangshan Mountain in the south and Wushan Mountain in the east, the water vapor cools and forms small water droplets in the rising process, that is, fog, and the clouds are thick, so the sun is blocked by water mist (clouds), so there are more cloudy days and fewer sunny days. The climate of Chengdu Plain belongs to subtropical humid monsoon climate. The annual average temperature is about 65438 08℃. The annual average precipitation is above 1000mm, and the annual rainy days are about 300 days, which is foggy, making it one of the regions with the most rainy days in China. However, because the plain is adjacent to the western Sichuan Plateau, it is deeply affected by the sinking of cold air in mountainous areas, and most of the river water in the plain comes from the melting water of snow and ice in the western plateau and mountainous areas. At the same time, in the low-lying ancient river area on the plain, the groundwater level is high and the soil is wet and cold. Therefore, the air temperature, water temperature and ground temperature in Chengdu Plain are low, and the thermal conditions are slightly worse than those in other areas of Sichuan Basin.