Why does it always rain in Tomb-Sweeping Day?

During the Qingming Festival, the weather gets warmer, the vegetation is lush, and the natural air is fresh and clean, so it is called "Qingming". April is really a rainy month. According to the analysis of relevant experts, around Tomb-Sweeping Day, the southern part of China was exposed to the sun for longer and longer, the temperature rose rapidly, and the warm and humid air flow in the southeast sea became active. At the same time, the influence of dry cold air in the north has not weakened, and it frequently goes south, often meeting warm and humid air from the south in Jiangnan or South China. In the first and middle days of April every year, the cold and warm air on the mainland is quite powerful, and the situation will last for a long time. The stalemate in Jiangnan or South China will cause continuous drizzle.

In meteorology, the interface between cold and warm air is called front. Above the front, the warm and humid airflow from the south is high and light, while the dry and cold airflow from the north is low and heavy, and the warm and light airflow is lifted by the dry and cold heavy airflow. After the warm and humid airflow climbs to the high altitude, the temperature drops and the water vapor condenses, forming clouds to rain. If the cold air is strong enough to push the warm and humid airflow to the sea, there will be clear skies under the control of cold air in the south of the Yangtze River.