What do you mean by "the third class of the Millennium"?

There are three waiting periods in the Millennium: "When the geese come, the mysterious birds return, and the birds are ashamed." This means that at this time, geese and swallows began to fly south to avoid the cold, and the birds stored "dry food" for the winter. Birds, as keen climate "forecasters", reflect the sharp change of temperature.

During the Millennium solar term, the summer heat gradually disappears, the autumn air is crisp, the osmanthus fragrance is fragrant, migratory birds such as Hongyan and Swallow begin to fly south to avoid the cold, and various birds begin to store food for the winter.

"Hongyan comes, Xuanniao returns." After the Millennium, migratory birds that are most sensitive to climate migrate collectively. Hongyan began to fly from the north to the south, and mysterious birds from the south also flew back to the north, and various birds began to store food for winter.

There is a saying in the folk proverb: "The white dew flies in the south in the autumn night", "When beginning of autumn knows it, it makes people sleep, and the sunflower laughs in summer, and the white dew returns to the wild goose, and the osmanthus fragrance fills the garden in the autumn equinox". Therefore, migratory birds like geese are regarded as a symbol of autumn.

Meteorological changes in the Millennium

The White Dew is the watershed of the summer heat, and "White Dew" represents the end of the summer heat. After entering the Millennium solar terms, the summer monsoon is gradually replaced by the winter monsoon, and the cold air gradually moves southward frequently. In addition, the position where the sun directly touches the ground moves south, and the sunshine time in the northern hemisphere becomes shorter and the sunshine intensity weakens. At night, it is often partly cloudy and sunny, and the ground radiation dissipates quickly, so the temperature drop is gradually accelerated. There is a saying called "Qiu Qiu in a thousand years, it is cold all night."

After the Millennium, the temperature difference between day and night gradually widened. Although the temperature is high at noon during the day, it is already very cold in the morning and at night. Starting from the Millennium solar terms, according to the standard of dividing the four seasons by climatology, all localities began to enter autumn one after another. At this time, the temperature difference between day and night in China can reach 8℃- 16℃, so the Millennium is a solar term with a large temperature difference in a year.

Baidu Encyclopedia-White Deer

Kaiyuan Radio and Television Station-Today's White Dew is also the solar term with the biggest temperature difference between day and night.