What is the plum rain in the south of China?

Meiyu in southern China belongs to frontal rain, which is controlled by quasi-static front.

After June every year, the summer monsoon that affects China moves northward to the middle and lower reaches of the Yangtze River. Because the cold and warm air masses are evenly matched, the front has been hovering in the middle and lower reaches of the Yangtze River for a long time, and the rain belt is also hovering here. There will be rainy weather in the middle and lower reaches of the Yangtze River, which may last for one month. This period is the season when plums are ripe, so people call this rainy weather plum rain.