Why is the temperature difference between Hunan and Guangdong so great?

The first is the latitude factor. Followed by topographic factors and climate factors. Hunan is in the north, Guangdong in the south, and Hunan is a hilly area. The influence of cold air from the south has weakened a lot, and it will be gone when it reaches Guangdong through the first piece of Nanling. Although both Hunan and Guangdong belong to subtropical monsoon climate, the inland of Hunan is more inclined to continental climate, and Guangdong is close to the sea, which is somewhat inclined to subtropical humid climate due to marine factors. Guangdong belongs to the Pearl River Delta Plain, and the tributaries of the Pearl River go deep into the hinterland of Guangdong, which is more susceptible to the warm and humid factors of ocean currents.