Why is there no hot weather in Lushan Mountain?

The peaks of Lushan Mountain are all above 1,000 meters above sea level, and the mountains are densely covered with forests and surrounded by rivers and lakes below. In addition, there is abundant rain all year round and high air humidity, which makes the temperature difference between the mountains and the mountains in summer large. In midsummer every year, the Poyang Lake Basin is scorching hot with the highest temperature reaching over 39°C. However, the average summer temperature in the mountains is only about 22.6°C, and the temperature in the morning and evening is often between 15-20°C.