At present, the four seasons are often divided according to the temperature change, and the method of "weather average temperature" by modern scholar Zhang Baokun is adopted. According to the four seasons divided by the weather average temperature method, the daily average temperature is equal to or lower than 10 degrees Celsius for five consecutive days, which is considered as entering winter.
Extended data:
Snow is an important symbol of winter in northern China. In the middle and lower reaches of the Yellow River in northern China and its vicinity, the snow in winter is often not as big as that in Xiaoxue solar terms. The main reason is that Xiaoxue solar terms are in front, the temperature is high, the total amount of water vapor in the air is larger than that in Daxue solar terms, and the possibility of heavy snow is greater.
In fact, the solar terms with the heaviest snow and the heaviest snow in the middle and lower reaches of the Yellow River and its vicinity are neither "light snow and heavy snow" nor "slight cold and severe cold" (because the temperature was lower and there was less water vapor in the atmosphere at that time), but the rainy solar terms in spring.
In winter, the climate is cold, and yin flourishes and yang declines. Affected by the cold temperature, the human body's physiological functions and appetite will change. Therefore, it is very necessary to adjust the diet reasonably and ensure the sufficiency of essential nutrients for the human body, so as to improve the cold tolerance and immune function of the elderly and make them overwinter safely and smoothly. Tonifying in winter is one of the traditional self-care methods to prevent diseases and strengthen the body and support the weak.
Baidu Encyclopedia-Winter