Why is there so much rain in the south of the Yangtze River, drought in the north of the Yangtze River, sand in the western regions, and snow in the north of the Great Wall?

1. Jiangnan is affected by the subtropical monsoon. In summer, the subtropical monsoon blows from the sea to the mainland, bringing abundant rainfall. Every year around April and May, the subtropical monsoon arrives in South China. In May, it lingers in the Jianghuai area for about a month, forming plum rainy weather. In June and July, it reaches the Yangtze River Basin, causing the Yangtze River to swell, and reaches North China and Northeast China in July and August. It exits the mainland in September, so the south is hot and rainy, while the north is dry and rainy. Spring drought occurs in North China and Northeast China, and wind and sand are strong in spring. This is because the direct point of the sun begins to move northward at this time, the northern hemisphere begins to warm, and the snow in North China and Northeast China melts. At this time, the wind is strong and the rain is less, so it forms Spring drought and sandy weather.

2. The Western Regions (the west of Yumenguan and Yangguan in Gansu are called the Western Regions) has a temperate desert climate. It is inland and the summer monsoon is difficult to reach. Since ancient times, there is a saying "Why does Jiang Flute blame willows? The spring breeze does not pass through Yumenguan" " said. There is much snow in Saibei because it is located in the Gaowei area, where winters are cold and rainfall mainly occurs in the form of snowfall.