The climate in China is "rainy and hot". Why is there a summer drought?

The hottest midsummer season in China's old calendar is called "dog days". Generally from mid-July to mid-August. At this time, the stationary front of Meiyu moved to the middle and lower reaches of Yokogawa River and northeast China in early July, and the middle and lower reaches of the Yangtze River were controlled by the "subtropical high", forming an anticyclone weather, which was dominated by underflow air, with long sunshine, strong solar radiation, high temperature and strong evaporation. Crops grow fast, and farmland needs a lot of water. However, due to the single air mass, except for thunderstorms in some areas, there is no big rain area, and generally there is dry and hot summer weather, so it is called "summer drought". In this season, the afternoon temperature in the middle and lower reaches of the Yangtze River generally reaches 33 ~ 35℃, and the high temperature as high as 43 ~ 45℃ appears in some places.