"Dog days" are the general name of the first, middle and last three days, and the dog days are the time when the temperature is the highest, humid and sultry in a year.

Liu Xi, a scholar in the Han Dynasty, recorded in Ming Jie: "He who squats, Geng Jin crouches under the summer fire. Jin is afraid of fire, so he squats down. "

Ban Gu, a historian of the Eastern Han Dynasty, also said in Hanshu: "Those who lie down say that Yin Qi will get up, but they are forced by the sunset and have not got up. Therefore, it is hidden because of the name. "