When does Huangmeitian usually start and end in Shanghai?

Meiyu period is generally in two solar terms, namely, grain sowing and off-season. The calculation method of ancient Meiyu period is that the first "three days" after the solar term of grain planting is the time of plum blossom, and the first "non-day" after the solar term in summer is the time of plum blossom.

The time of 202 1 Shanghai Huangmeitian is between June 7th and July 10.

Every year from late April to early May, 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 May, 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. During this period, due to the combined influence of cold and warm air, the front stayed in Zhu Jiang.

Rice yellow plum

In some years, Huangmei days in the middle and lower reaches of the Yangtze River seem to have passed, the weather turned fine and the temperature rose, showing the characteristics of midsummer. However, a few days later, hot and humid thunderstorms and showers reappeared and remained for quite some time. This situation is like Huangmeitian returning to the middle and lower reaches of the Yangtze River, so it is called "Huangmeitian".

"It thunders in midsummer and Huangmei hangs upside down" is a weather proverb widely circulated in the middle and lower reaches of the Yangtze River. It means that after the meiyu has passed, if there is thunder in the "light summer heat", the meiyu will be reversed.

Generally speaking, the duration of "pouring Huangmei" is very short, ranging from about one week to ten days and a half months. However, during the "Huangmei" period, due to many thunderstorms and showers, the rainfall is often quite concentrated, which needs attention. Because "inverted yellow plum" is a kind of plum rain, it usually turns into sunny and hot weather after it ends.

From the various plum rains described above, we can see that Huang Meiyu, which is usually considered to be similar, is actually diverse, and the differences between them are sometimes quite large. Compared with normal plum rain, early plum, late plum, extremely long plum rain, empty plum and severe yellow plum all belong to abnormal plum rain.