bai-u

(Also called tsuyu.) In southern Japan and in parts of China, the name of the season of heaviest rainfall.

The bai-u season (June and early July in Japan, May to July in China) is the most important period for the cultivation and transplanting of rice.The bai-u rains are also called plum rains or mold rains, with reference to the season when plums ripen and to the effects of continued dampness.

A division of the year according to some regularly recurrent phenomena, usually astronomical or climatic.

Any function of time f(t) is periodic with period t if f(t) = f(t + τ) for all times t, where τ is the smallest number for which this equality holds.