During the Meiyu period, the Meiyu front system and the main rain belt obviously moved out of the middle and lower reaches of the Yangtze River. If there are less than two rainy days in the five days in this area, the maximum temperature of each station in this area will obviously rise above 30℃, and the southerly wind speed on the ground will also obviously increase, so it will be designated as plum blossom. China's current almanac uses the statement of Shenshu Jing, saying that after the slight summer heat, plum blossoms will bloom between July 8 and 19.
The weather-confirmed plum discrepancy is different from that in the almanac. Meteorologically, the division of plum blossom into plum blossom, out of plum blossom and rainy season is based on the weather circulation situation of Dafanwang. Geographical distribution characteristics of weather system, geographical distribution position of precipitation and changes of meteorological elements.
Because the evolution of circulation situation is not consistent or the same every year, there are complex differences in meteorology, plum blossom date and plum blossom period. When the Meiyu front area and its rain belt reach or form in the middle and lower reaches of the Yangtze River or the Jianghuai area, it is called Meiyu. The period when the rain belt is stagnant or wandering is called Meiyu period; When the rain belt rises northward and reaches the Yellow River basin steadily, and the Jianghuai area is controlled by the western Pacific subtropical high, the plum rain in the Jianghuai area ends, that is, plum blossoms appear.