At this temperature, people are the most suitable for survival. But usually the outside air temperature is much lower than this temperature.
Therefore, people will feel very comfortable at a temperature close to 40 degrees, and their pores will expand. This also gives people a comfortable feeling.
On the other hand, it is psychological. Sunlight usually symbolizes good weather. It nourishes the growth of everything, and light energy brings hope to people. Sunlight is a necessary condition for survival. Similarly, when it thunders and rains, people's mood will be low, but when it is sunny, their mood will be better. That's why they want to run and jump.