2. The origin of the long summer solar term: Long summer is the seventh solar term among the 24 solar terms and the first solar term in summer. Long summer indicates the change of seasons and the official start of midsummer season. When the sun reaches 45 degrees of the yellow meridian, it is a long summer, usually on May 5 or 6 of the Gregorian calendar every year. After the long summer, the temperature in southern China rose rapidly, and the rainfall and days of rainfall increased significantly.