Why is the north latitude high and the temperature high in summer?

The energy of the sun should be the main reason for the high temperature in summer, and the sunshine time is: it is the height angle of the sun and the latitude of the direct sun. The energy received per unit area is directly proportional: therefore, the negative number is south latitude and the positive number is north latitude. Because extreme day and night need to be considered separately, only 60 S ~ 60 N is drawn. The temperature in high latitudes drops a little slowly, because we only consider the energy harvested per unit area at this moment, and do not consider the accumulated temperature, subtropical high and summer monsoon. This conclusion is not bad in summer in China (the sun is about 20 degrees north latitude). Chongqing, Wuhan and Nanjing, the three "stoves" in China, are all cities in the Yangtze River basin, not particularly at the southern end, but their extreme maximum temperatures all exceed 42℃, and Beijing's extreme maximum temperatures are also above 4 1℃. On the contrary, Guangdong and Hainan, the southernmost tip of China, rarely have high temperatures above 40℃. Of course, there are many high temperature factors. It is related to the topography, climate and population of the city, but in the hottest summer, the temperature in most cities in China is above 30℃, and it is an indisputable fact that it is not obviously hotter in the south. Personally, in a nutshell, the main reason is that in summer in the northern hemisphere, the sunshine time in the north is longer than that in the south, which makes up for the disadvantage of low sun height to receive heat, while in winter in the northern hemisphere, the sunshine time in the north is more than that in the south. China is in the northern hemisphere. Consider two locations, Beijing and Guangzhou. The latitude of Beijing is 40 degrees north latitude and Guangzhou is 23 degrees north latitude. Whether in winter or summer, the solar altitude angle in Guangzhou at noon is higher than that in Beijing, but it can also be seen that the advantage of solar altitude angle in summer is not obvious in winter.