First of all, Nanning is located in the subtropical climate zone, which is easily affected by a single rain mass, especially in summer. These rain clusters usually appear in the environmental field where the vertical distribution of water vapor and unstable stratification is extremely uneven, thus causing strong convective rainstorm.
Secondly, the meeting of cold air and warm moisture mass will also lead to rainfall. When cold air masses from Siberia and Mongolia meet and combine with warm and humid air masses from the Pacific Ocean and the Indian Ocean, due to their different temperatures and humidity, a large amount of precipitation will be generated. This kind of confrontation and interaction between cold and warm air is particularly obvious in the rainy season in Nanning, which leads to frequent rainfall.
The above are the main reasons for the rain in Nanning these two days. I hope it will help you.