Summer is the height of Yang energy, which is moving, bright, light and hot in comparison to Yin, which is still, dark, dense, and cool.
Yin and Yang are in a constantly dynamic relationship with each other, and as one reaches a peak, the seed of the other is born, and begins blooming as the other wanes. Yin nourishes Yang, as Yang motivates Yin.
This is the natural order of things reflected in the dynamic cycle of Yin Yang. The key to understanding this relationship is to see it as animated, in motion, and constantly changing from one to the other. Chinese Medicine recommends cultivating Yang energy in spring and summer, while protecting Yin energy in autumn and winter.