Why is it hot and cold in February and March?

First of all, during this period, the direct point of the sun is constantly moving northward, the sunshine time in the northern hemisphere is slowly prolonged, and the atmospheric temperature is also slowly rising, which means that the temperature is gradually rising. Moreover, the Siberian high is gradually weakening, but because the Siberian-Mongolian high still exists, it does not go south from time to time, resulting in a cold wave in spring, which is what we call "late spring cold". Because the gradual increase in temperature is a general trend, and the cold air going south is only from time to time, there will be a phenomenon of hot and cold. The northern proverb says that "it will be cold in the last ten days in Tomb-Sweeping Day". Even in April, Mongolian high pressure may continue to affect the northern region!