The rain, snow and frost come from water, but they are different. Frost is the direct condensation of water vapor in the air, which forms white crisp ice crystals on the ground or near ground objects with a temperature below zero degrees Celsius. The formation of frost is closely related to air temperature. The climate in China is quite different from place to place, and the early frost in autumn generally moves from north to south. In autumn, the temperature drops early and quickly in the north. The first frost generally occurs in the northern part of Northeast China in early September, and in the southern part of Northeast China and North China in mid September to late October. The temperature drops late in the south, and the middle and lower reaches of the Yangtze River mostly show the first frost in the middle and late November, while the northern and central regions of South China only show the first frost in December. People often use the difference between the highest temperature and the lowest temperature to represent the temperature difference between day and night. According to the analysis of meteorological data in the past 10 years, the temperature difference between day and night in frost falling solar terms across the country is 11.6 ℃, which is similar to the temperature difference between day and night in the autumnal equinox and cold dew solar terms. It can be seen that the temperature difference between day and night is not the largest in all solar terms. The reason why people feel that the temperature difference between day and night during the frost season is large is that we experienced a long summer heat before the frost season came. With the advent of the frost season, cold air activities began to be frequent, the light was stronger in the day, and the temperature dropped significantly at night, increasing the temperature difference between day and night. (Outlook New Times)