What weather system causes heavy rain during Qingming Festival?

The heavy rain during the Qingming Festival is a quasi-stationary frontal weather system, mostly caused by the weakening of the cold front.

The weather is similar to the first type of cold front, except that the front slope is smaller and the cloud area and precipitation area are wider. At the beginning of each summer, the warm and humid air from the ocean collides with the cold air moving south from the continent, forming a famous weather system in the middle and lower reaches of the Yangtze River and the Huaihe River Basin - the Jianghuai quasi-stationary front.

South China quasi-stationary front

Mainly active in the Nanling Mountains or the South China Sea. It can be seen all year round, but it mostly appears in winter and spring, with the least occurrence in autumn. Precipitation is not strong in winter, but heavy rains can occur in spring and summer, lasting for several days or even more than 10 days. The position of the quasi-stationary front in South China changes with the seasons. In the winter half of the year, the cold high pressure on the north side of the front is strong, causing the frontal area to move southward; in the summer half of the year, the subtropical high pressure on the south side of the front is strong, making the frontal area move to the north.