Weather of Mangzhong (Grain in Ear)
The plum rain season in the middle and lower reaches of the Yangtze River mostly begins in the later part of the Mangzhong solar term. Farmers are very concerned about the rain during this period, so many meteorological proverbs have been passed down. For example:
◇ Mangzhong and Xiaizhi are water seasons; if there is no rain, it will be a dry day (Yue).
◇ Mangzhong and Xiaizhi, water floods the rice fields (Yue).
◇ If it rains during Mangzhong, the water will rise during the Dragon Boat Festival (Xiang).
◇ Frequent rain during Mangzhong and Xiaizhi means typhoons will be late; little rain during Mangzhong and Xiaizhi means typhoons will come early (Min).
◇ During Mangzhong and Xiaizhi, one needs to be led by another when walking (Su, Wan, Chuan, E, Gui) (referring to the many overcast and rainy days, which make roads slippery).
Generally, in the later part of the Mangzhong solar term, a period of continuous rainy weather occurs from the Yangtze River basin in China to southern Japan. As this coincides with the ripening of plums, it is called "plum rain" (meiyu). The most famous poem describing the plum rain from the "Thousand Poems Collection" is Zhao Shixiu's "Waiting for a Guest": "In the plum rain season, every household has rain; In the green grass ponds, frogs croak everywhere. My guest did not arrive after midnight, So I idly tapped my chess piece and the lampwick fell."
According to statistics on the start date of the plum rain season from the book "Climate of the Middle and Lower Reaches of the Yangtze River": Wuhan generally starts on June 16th, Anqing in Anhui on June 15th, and Nanjing and Shanghai on June 17th. In most of Hunan, Jiangxi, and Zhejiang, the plum rain usually arrives a few days earlier than in the Yangtze River basin. However, years with very few rainy days have also occurred. In meteorology, a period without continuous precipitation during this time is called a "plum rain skip" (kongmei). After the plum rain season comes the summer drought period in the middle and lower reaches of the Yangtze River. If there is a plum rain skip, this region may experience a severe summer drought.
During Mangzhong, although the flood season in South China is in its late stage, heavy downpours can still occur. Normally, Hunan, central Jiangxi, and southern Zhejiang are the first to enter the plum rain season. After it begins, the main flood season in these areas starts, similar to South China, with occasional heavy rainstorms. Mountainous areas need to be警惕 (alert) to secondary disasters such as flash floods and mudslides caused by local heavy downpours. Urban drainage, farmland waterlogging relief, and rescue of victims are also included in emergency response plans.
In history, the torrential rains during the plum rain seasons of 1954, 1991, and 1998 all triggered catastrophic floods throughout the entire basin. According to statistics on flood and drought disasters released by the Office of the State Flood Control and Drought Relief Headquarters in May of this year, the 1998 floods resulted in 4,150 deaths and economic losses of 255 billion RMB. Of course, the formation of such a situation is certainly due to the strong and evenly matched forces of cold and warm air masses.
In addition, the southwestern region also enters its rainy season of the year starting in June. At this time, hail weather begins to increase in the highland areas of western Southwest China.
During this period, except for some areas like the Qinghai-Tibet Plateau and the northernmost part of Heilongjiang that have not yet truly entered summer, people in most areas can generally experience the heat of summer. In Nenjiang, located in northern Heilongjiang, the hottest day in 30 years from 1971 to 2000, 37.1°C, occurred during the Mangzhong period.
In June, both in the south and the north, there is a possibility of temperatures exceeding 35°C. The Huanghuai region and the eastern part of the Northwest region may see temperatures above 40°C, but it is generally not a sustained heatwave.
In Taiwan, Hainan, Fujian, and the Liangguang region of South China, the average temperature in June is around 28°C. If it is before a thunderstorm, the air humidity is high, and it can be both muggy and hot. Sometimes, high-temperature forecasts need to be issued to the public to remind them to prevent heatstroke, air-conditioning sickness, and acute gastroenteritis.