2. The specific date of Sanfu is determined by the date of the solar term and the date of the dry branch. According to the traditional calculation method in China, the third and fourth Geng days after the summer solstice are the start dates of the first (head-lying) and the middle (second-lying) respectively, and the first Geng day after beginning of autumn is the first day of the last (third-lying).

3. The dog days appear between the summer heat and the summer heat, which is the day with the highest temperature, humidity and sultry weather in a year. The reason for the high humidity in dog days is that the southeast wind blows in dog days, while the Pacific Ocean and Indian Ocean are in the southeast. The air is humid, and the humidity of the wind causes the high humidity in dog days. In late autumn or winter, on the contrary, the northwest wind blows, while the northwest is dry inland, blowing dry cold wind to the mainland, so the humidity in winter is low.