People call the wind that blows when flowers are blooming "flower trade wind", also known as twenty-one, because it is the wind that coincides with the flowering period, which means the wind that carries the news of flowering. This is recorded in Zhang Dai's work "Night Sailing" of the Ming Dynasty. A poem by Xu Shichuan of the Tang Dynasty said: "One hundred and fifteen days of cold food and rain, twenty-four flowers and trade winds." "The Chronicles of the Year" said: "There are two weathers in January and six weathers, from Xiaohan to Guyu. In April, there are eight weathers and twenty-four weathers, five days each, with the wind of a flower." - Sogou Encyclopedia