In the Gregorian calendar,the White Dew usually falls around September 7, and more often refers in particular to the day when the sun is exactly at the celestial longitude of 165°. It is the day when the temperature drops sharply, the rain never stops, and the duration of the sunshine decreases substantially. Therefore, the date reflects the transition from summer to autumn. Normally, a period of cloudy and rainy weather occurs after White Dew.
During the White Dew, there are different weather conditions in different parts of China. In the north, the hot summer has ended, dew begins to fall, wild geese begin to migrate to the south, and birds begin to stock food for the long winter. Yet, it may still be very hot in the south. The Yangtze River and Huaihe River valleys are usually very humid during this period. Customs related to the White Dew also vary greatly from one area to another. For example, people in Fuzhou Fujian Province often eat longans to build up their health on this day while residents living around Taihu Lake in Anhui Province hold a ceremony to worship Yu the Great (the legendary founder of the Xia Dynasty and the ancient hero who successfully controlled floods).