Yudu Nal

Yudu Nal

15th day of the sixth lunar month
Yudu, which means "washing one's hair in flowing water," is a tradition that goes back to the Silla period (7th-9th centuries) in Korean history. It has been the custom on this day to go on picnics near a moving body of water, a stream, river, or waterfall, and to bathe and wash one's hair. Folklore has it that doing so will ward off fever and other heat-related ills. In any case, swimming in a cool stream is a refreshing way to beat hot summer weather. In modern times people also call this activity mulmaji, "greeting the water."
SOURCES:
AnnCustKorea-1983, p. 117
FolkWrldHol-1999, p. 416