Why is it so hot in Jiangsu, Zhejiang and Shanghai that Hong Kong is much cooler when it is close to the equator?

The main reason of high temperature in Jiangsu, Zhejiang and Shanghai in summer is the influence of subtropical high. Subtropical high pressure is a high pressure system formed in subtropical areas, which will lead to the sinking of airflow and form high temperature and dry weather. In summer, the subtropical high usually strengthens and moves northward, thus affecting South China, including Jiangsu, Zhejiang and Shanghai.

Compared with Jiangsu, Zhejiang and Shanghai, Hong Kong is closer to the equator, but why is it much cooler? This is mainly due to the following factors:

1. Sea-land difference: Hong Kong is located in the Pearl River Estuary, a coastal city with the characteristics of maritime climate. In contrast, Jiangsu, Zhejiang and Shanghai are located inland and far from the ocean, and are less affected by the maritime climate.

2. Topographic factors: Hong Kong's topography fluctuates greatly and the terrain is relatively high. In summer, there are peaks blocking the southeast monsoon, which slows down the wind speed of the city and thus lowers the temperature.

3. Urban heat island effect: Urban heat island effect refers to the phenomenon that the temperature of the city is higher than that of the surrounding countryside. As economically developed areas, Jiangsu, Zhejiang and Shanghai have a high degree of urbanization and obvious urban heat island effect, which leads to high urban temperature.

Therefore, although Hong Kong is close to the equator, it is relatively hot in summer in Jiangsu, Zhejiang and Shanghai due to land and sea differences, topographic factors and urban heat island effect.