In summer, the weather in northern cities such as Shijiazhuang is sultry. Please explain the reason with astronomical knowledge.

The influence of subtropical high region

Subtropical high is a high pressure between tropical and temperate zones. This high pressure is a large-scale weather system that controls tropical and subtropical regions for a long time, and its position and intensity change with seasons. In the area controlled by the high-pressure center, due to the sinking of airflow, there are generally less clouds and more rain, and there are many precipitation weather systems on its edge.

The subtropical high affecting China mainly includes the western Pacific high, the Qinghai-Tibet high and the South China Sea high. For the north, it is mainly the influence of the western Pacific high. And in summer, the airflow sinks and it feels stuffy.