When is the rainy season in Jiangnan?

In early summer, there are often long rainy days in the Jianghuai basin. At this time, the utensils are easy to be moldy, so it is also called "moldy rain" or "mildew" for short; It is also called "Plum Rain" or "Huang Meiyu" because it is the time when plums south of the Yangtze River are ripe.

The middle and lower reaches of the Yangtze River in China are usually rainy from mid-June to early July every year. In the past few days, the sky has been gloomy and the precipitation has been constant, sometimes big and sometimes small. Therefore, there is a popular proverb in southern China: "Rain hits plum blossoms, and there is no sun for forty-five days". Continuous rain, high temperature and high humidity are the main characteristics of plum rain.

Calculation method:

According to the principle of combining circulation conditions with regional precipitation, from late May to early July, the ground peak activity is frequent within the range of 29-33 north latitude, with six rainy days for two consecutive periods. At the same time, referring to the lower reaches of the Yangtze River, the average temperature of each station is basically stable above 22℃, which is the start date of entering Mei. In the time curve of rainy days, rainfall, cloud cover and other climatic factors in early summer, there are also days that suddenly increase (that is, there is a turning point), which is regarded as the average plum blossom period.

Traditionally, in China, the judgment of plum entry and plum exit is based on the combination of solar terms and branches. According to the calendar, the first third day after mango seeds is plum blossom, and the first last day in Xia Hou is plum blossom. If the weather on the awning day is C, it is designated as entering the plum blossom, and if it is not in the shallow summer, it is designated as leaving the plum blossom.

In ancient China, there were several rules for entering Mei. In trivial records, "(Min people) entered Mei on Geng Day in Xia Hou." "Shenshu Jing": "After the awn is planted, it will enter the plum in three days." "Jiangnan Record": "Plant mangoes in May, and meet your wife and enter Mei." "Tian Wu Jia Xing": "The rain after the awn seed is Huang Meiyu", and the awn seed is considered as plum blossom. There are two reasons for the above differences: first, regional differences; Second, the date of entering Mei for many years often changes. At present, in the almanac of our country, the saying of Shenshu Jing is adopted. In the weather analysis and forecast, it often refers to the day when the weather situation turns to Meiyu situation.

For example, on June 6, 2006, mango seeds will enter Mei on the same day. July 17 coincides with a weekend after the intense summer heat, so the plum blossom date in 2006 is July 17. Huangmeitian ***42 days.