What is the origin of the sentence that a slight cold is followed by a heavy cold, and wheat seedlings will spend the winter?

65438+10.5 is the "slight cold" in the 24 solar terms. When the sun meridian reaches 285 degrees, the slight cold solar term begins. Around March 9th, as the saying goes, "heat is in dog days and cold is in dog days", slight cold and severe cold make it the coldest season of the year. During the slight cold solar term, the East Asian trough developed the strongest and most stable, the Mongolian cold high and Aleutian low also reached the strongest and most stable, and the ridge scale of the westerly trough reached the maximum, which matched the strongest westerly intensity. The cooling process of cold air is frequent in the slight cold season, but few of them reach the cold wave standard. Proverbs used to make long-term forecast according to the temperature of slight cold are "slight cold is not cold, clear the mire" and "slight cold is cold enough, and it will be warm next spring". The slight cold weather is sunny and warm, which indicates that it will be very cold next spring.