White Dew is the season of fall.

White Dew is the 15th of the 24 Solar Terms, the third solar term in the fall, and the end of the month of Shen and the beginning of the month of You in the dry calendar. The Do refers to the decan; the sun reaches 165 degrees of yellow longitude; and the festival is intersected on September 7-9 of the Gregorian calendar.

"White Dew" is an important festival reflecting the growth of cold in nature. As the cold air turns from defense to offense, the day is still hot with sunshine, but the temperature drops quickly after evening, and the temperature difference between day and night gradually widens.

Time to white dew, summer winds are gradually replaced by winter winds, cold air to attack, coupled with the sun's point of direct sunlight to the south, the northern hemisphere sunshine time becomes shorter, the intensity of light is weakened, the ground radiant heat dissipation fast, so the temperature drop is gradually accelerated.

White Dew basically ended the sweltering heat of the summer days, the weather gradually turned cooler, cold dew condensation. The ancients to four times with five elements, autumn is gold, gold white, white to describe the autumn dew, so the name "white dew".

Weather changes

After entering the White Dew season, the summer winds are gradually replaced by winter winds, cold air south gradually and frequently, coupled with the location of the sun directly above the ground to the south, the northern hemisphere sunshine hours become shorter, the intensity of sunshine weakened, the night is often clear and less cloudy, the ground radiation heat dissipation, so the temperature drop is also accelerated gradually, there are "White Dew Autumn Equinox Night, one night cool night" said.

After the White Dew, the temperature difference between day and night is gradually widening, the daytime temperature at noon is higher, but the morning and the night has been a slight coolness. According to modern scholars Zhang Bao Koon proposed "wait for the average temperature" divided into four seasons of the standard, wait for the average temperature of 10-22 ℃ during the spring or fall.

According to this standard, from the beginning of the White Dew Festival, all over the world began to enter the fall. At this time, the temperature difference between day and night across China can reach 8 ℃ -16 ℃, so the White Dew is a large temperature difference between the seasons of the year.