Why is the weather in Changsha hot and cold?

In the nature of the area related to bad weather and air passage, the so-called weather "air mass" means that the air quality at that time is cold-resistant, that is, when cold air is passed through the mouth, the weather gets worse and the body temperature drops, so it will feel cold; On the contrary, when the air quality is warmer, it is verbally said that when warm air passes through the border, it will feel hot when the weather is fine and the temperature rises. Due to the alternating cold and warm air on the earth, mainly the cold air generated at the two poles of the earth, warm and humid airflow is generated at the equator of the ground, which interacts and promotes each other, thus in cold and hot weather!