When is the first frost?

Every year around Gregorian calendar1October 23rd, when the sun reaches longitude 2 10 degrees, it is a transitional solar term from autumn to winter. There is a lot of heat dissipation on the ground in autumn, and the temperature suddenly drops below 0 degrees. The water vapor in the air directly condenses on the ground or plants to form tiny ice needles, and some become hexagonal frost flowers with white color and loose structure, so it is called the first frost.

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".

During the first frost period, it usually lasts from late June 10 to1early October 10. As dry and cold air gradually dominate the whole country, warm and humid air is marginalized, and many weather with characteristics of summer and early autumn exits, so the weather is relatively simple. Before and after beginning of winter, there were often strong winds and cool weather, and some places entered winter in a short time.