Is it still cold on May 9th?

It's getting colder. The number nine is a folk method for calculating the dates of cold spring and warm bloom in China. It usually starts from the solstice in winter, and every nine days is a "nine", and so on. Among them, the number "May 9th" happened just before and after the solar terms in beginning of spring, and its climate is characterized by large temperature difference between day and night and frequent cold air activities. Westerly jet, the southern branch of East Asia, began to weaken, and the cold climate was coming to an end. However, the intensity and location of westerly jet, the northern branch, remained basically the same, and gale cooling was the main prevailing weather, so it was still cold during May 9th.