Long summer is the seventh of the 24 solar terms and the first in summer. The festival of long summer falls on May 05-07 of the Gregorian calendar every year, when the bucket handle of the Big Dipper points to the southeast and the longitude of the sun reaches 45. "Almanac": "Dou refers to the southeast, Wei is the long summer, and everything has grown up since then, so it is named long summer." Long summer is an important solar term, marking the peak season for the growth of all things. After the long summer, the sunshine increases, the temperature rises gradually, the thunderstorm increases, and the crops enter a vigorous growth stage.

Chang Xia said that saying goodbye to spring is the beginning of summer. Spring comes and summer grows, autumn harvests and winter storage, and in the long summer, everything is thriving. Because China has a vast territory and a large span from north to south, natural rhythms vary from place to place. In the long summer season, only the area south of Fuzhou-Nanling line in China is the real summer of "the trees are dark and the summer is long, and the balcony reflects into the pond"; And some areas in the northeast and northwest have just entered spring. According to the classification standard of modern climatology (climate average temperature) in China, the daily average temperature rises steadily to above 22℃, starting in summer.