The first frost is the eighteenth of the twenty-four solar terms and the last solar term in autumn. Fight with your fingers; The solar calendar is 210; Celebrate every year on 10/23-24 of the Gregorian calendar. After entering the first solar term in first frost, the scene of late autumn is obvious, and cold air moves southward more and more frequently. The first frost does not mean "frost", but refers to the sudden drop in temperature and the large temperature difference between day and night. On the national average, "first frost" is the season with the largest temperature difference between day and night in a year.
Historical origin
The first frost is the last solar term in autumn and the transition from autumn to winter. In the first frost season, everything is finished, everything goes to heaven, the sun goes to the ground, and the yin begins to condense. The cold weather began with the first frost. Yizhoushu Zhou said: "Autumn and March are empty: summer, autumn equinox, first frost."
In Lun Heng, Wang Chong of the Eastern Han Dynasty said: "Clouds and fog are also signs of rain, while summer is dew, winter is frost, temperature is rain, cold is snow, and rain and dew are frozen, all from the ground, not from the sky." Whether it is dew or frost, "it comes from the ground, not from the sky." How can it be called first frost? In fact, the name "first frost" is only used to describe the climate characteristics of "sudden drop in temperature and large temperature difference between day and night" in this season.
Because "frost" is a manifestation of cold weather and large temperature difference between day and night, it is named "first frost" to indicate that "the temperature drops suddenly and the temperature difference between day and night is large".
The "first frost" solar term reflects the climatic characteristics of the cold weather, but it does not mean that it will be "frost" when entering this solar term. In fact, "frost" didn't fall from the sky. The "frost" is the condensation of water vapor on the ground when it meets cold air due to the change of temperature difference. The solar term "first frost" has nothing to do with "first frost".