Why is it rainy in Sichuan Basin?

There are many rivers in Sichuan Basin, with high terrain in the northwest and low terrain in the southeast. The southeast monsoon carrying a lot of water vapor was blocked by the mountains in Sichuan basin, forming topographic precipitation.

Sichuan Basin is located in the subtropical zone, with a warm and humid climate. In addition, the cold weather is blocked by the Qinling Mountains in the north, so the evaporated water vapor in the basin cannot escape and continues to gather in the basin to form rainfall. As a result, a lot of rainy weather has appeared in this area, which has become the area with the least sunshine radiation in China.