Why are Wuhan, Nanjing and other cities along the Yangtze River so hot in summer?

China's "three stoves" are located in three famous cities along the Yangtze River: Chongqing, Wuhan and Nanjing. It's very hot all day, even the lowest temperature is very high and hot, and the lowest temperature is around 28 degrees most days. According to the research of the Meteorological Observatory, the highest temperature in a day is ≥35 degrees, which is called "hot day", and the number of hot days in the three cities is as many as 15~35 days a year. Among them, Chongqing is the hottest. Historically, the highest temperatures in the three cities were mostly above 40 degrees. Therefore, it is called "three furnaces". Why are these three places so hot?

First, in July and August every year, as soon as the plum rains pass in the middle and lower reaches of the Yangtze River, the high-pressure temperature control here makes the low-level airflow move to form clouds and rain during the summer drought, and the surface temperature is very high. According to the measurement, the highest temperature on the ground in hot weather can reach 65 ~70 degrees.

Second, the three famous cities are located in the valley of the Yangtze River basin. At low altitude, the ground temperature and heat are not easily lost, so most of the heat is preserved. In addition, the air flows into the valley from the high terrain, unable to form clouds and rain, and the temperature is getting higher and higher. At the same time, rice fields crisscross along the Yangtze River, with dense river networks, oxygen-rich air and high humidity. The high temperature and high humidity climate makes it difficult for human sweat to evaporate, which makes people feel very stuffy.

Thirdly, due to the lack of cool breeze here in summer, the airflow is mainly downward, and the atmosphere is very stable, even without a trace of wind, which accelerates the hot atmosphere here.