Why is it called rainy season

In early summer, there are often long rainy days from the middle and lower reaches of the Yangtze River to southern Japan. Plums in the south of the Yangtze River are ripe, so they are called "Plum Rain" or "Huang Meiyu". So the temperature is high, the humidity is high, the wind speed is low, the light is scarce, and the utensils are prone to mildew, so it is also called "mildew rain". The name "Meiyu" comes from a meteorological term in China and was called Huang Meiyu in ancient times.

In history, "Huang Meiyu" usually refers to the precipitation of "Mei" Festival. People in the middle and lower reaches of the Yangtze River are used to taking the solar term "Mangzhong" as the May Festival, which coincides with the mature season of plums, so it is also called "Huangmei". Meteorologically, Meiyu is a unique climatic phenomenon in the process of seasonal transformation of atmospheric circulation in East Asia at the turn of spring and summer, which can be divided into typical Meiyu and early Meiyu.

Reasons for rainy season:

Every year from late May to early June, cold air from the north and warm air from the south meet in South China, forming a quasi-static front in South China. By the end of June, the influence of warm air was strengthened, and the quasi-static front moved northward to Jianghuai area, becoming the quasi-static front of Jianghuai (also known as Meiyu front). Because the warm air from the south carries a lot of water vapor, when it meets the cold air mass, it will produce a lot of convection activities. Because of the equal influence of cold and warm air during this period, the front stays in Jianghuai area.