What does cold dew mean?

The arrival of the cold dew solar terms means that autumn has arrived.

Cold dew literally means: "cold" means cold, while "dew" refers to the phenomenon that water vapor condenses into dew near the ground. From the meteorological point of view, the cold dew solar terms, like the white dew and the first frost solar terms, show more obvious significance of heat change than its moisture change, and more reflect a process of temperature change and seasonal change. In the cold dew season, Nanling and its north area have entered autumn, and the northeast and northwest areas are about to enter winter.

The solar term from the cold dew to the back of the first frost is only a short 15 day, but it is a period of time in a year when the temperature drops rapidly. After a cold air, it is common that the daily average temperature drops by 8℃ and 10℃. Therefore, this season is the turning point of climate change in many parts of China.

Historical origin

Cold dew is the end of the full moon in the dry calendar and the beginning of the full moon. At night, looking up at the starry sky, you will find that the "Big Mars" (Antares) representing midsummer has sunk into the west. After the cold dew, the height of the sun continued to decrease and the temperature gradually decreased. Cold dew is called "cold dew" because the temperature is much lower than that of Bailu solar terms, and cold produces dew condensation. "Twenty-four solar terms" said: "In September, the dew is cold and will condense." At this time, the temperature is lower than when it is "white dew", with more dew and chill day and night.

There is a proverb in China called "Dew first turns white and then cold", which means that after the dew festival, the dew turns from a little coolness in early autumn to a little coolness in late autumn.

There is also a proverb about cold dew: "Cold dew spans three dynasties, and you need to find a bridge after crossing the water", which means that the weather is already chilly and you can't wade across the river or go to the fields barefoot as before. During the cold dew, people can obviously feel the change of temperature difference. From white and crystal dew to freezing cold, it vividly reflects the continuous decline of temperature. As the cold intensifies, everything becomes dim.