The origin of long summer solar terms

Long summer is a solar term established at the end of the Warring States Period (239 BC), which indicates the change of four seasons and the beginning of summer in four seasons.

In fact, according to the standard of climatology, the daily average temperature rises to above 22℃ steadily, starting from summer. Before and after the "Long Summer", only the area south of Fuzhou-Nanling Line in China is really "the trees are dark in midsummer, and the balcony reflects the pond", while some areas in the northeast and northwest have just entered the spring, and the average temperature in most parts of the country is around 18 ~ 20℃, which is ". In May, Sophora japonica blooms in many places. In the long summer, everything is thriving.