Xiazhi occurs at celestial longitude 90°, around June 21-22. The northern hemisphere's longest day; yang energy reaches its annual peak. Classical wisdom warns: at peak yang, yin is born — heat will increase, but the seed of decline is planted.
Tradition: eating cold noodles, dumplings; rituals to thank the heavens for harvest. Climate: hottest days are still ahead — the "three fu" period typically follows.