Why does it always rain before and after Tomb-Sweeping Day?

Qingming is an important solar term in the China lunar calendar. It means that the weather is in the cold winter. Spring has come, and cold air from the north covers the south of China in winter. The cold air is very dry and there is little rain. When spring comes, warm air from the ocean becomes active. When warm air meets cold air, it will form rainy weather. Before and after Tomb-Sweeping Day, it happened that cold air and warm air met in the south, so it often rained.

In addition, there are many low pressures in spring in Jiangnan area. The clouds in the low pressure move fast, the wind is strong and the rain is urgent. Whenever the low pressure passes, there will be rainy weather. Also, before and after Tomb-Sweeping Day, there was a lot of water vapor in the atmosphere in the south of the Yangtze River, which easily condensed into Mao Mao rain at night, so there were many rainy days in Tomb-Sweeping Day.

In fact, during my stay in Tomb-Sweeping Day, there was not only much rain, but also changeable weather. It is often at noon, and it is still sunny, which makes people feel that "the warm wind makes tourists drunk". However, at night, the cold air suddenly went south, making people feel cold, as if they were back in winter. Therefore, there is a saying that "you must bring three seasons clothes when you go out in spring", which makes the most appropriate metaphor for the changeable weather in spring. In fact, it is really necessary to travel.