Uki, Tsuyu, and Akisame: Rainy Season in Japan
Spanning from May to July, Tsuyu (梅雨), also called Baiu (梅雨), is a cloudy/rainy season broadly seen in East Asia, including the southern part of China, South Korea, Taiwan, and Japan.
Tsuyu (梅雨) and Uki (雨季)
In Japan, almost all areas except for the northernmost island of Hokkaido experience that cloudy, rainy period.
Entering the season is called Tsuyuiri (梅雨入り) or Nyubai (入梅), which, based on the Japan Meteorological Agency, begins with the country’s southernmost prefecture Okinawa annually early in May.
On the other hand, finishing the season is Tsuyuake (梅雨明け), also known as Shutsubai (出梅), which ends in the northern Tohoku region annually around the end of July.
One theory holds that the reason why Tsuyu (梅雨) includes the word Ume (梅) in its name is that the plum fruit ripens during the rainy period,
and as you can see from the other word Ame (雨), meaning rain, Tsuyu is an Uki (雨季).
As Uki (雨季) means rainy season in Japanese, it represents long periods of rainfall, usually spanning over one month,
and the representatives in Japan are Tsuyu and the Autumn Rain Akisame (秋雨) seen from late August through around October.
(Reference Pages: Wikipedia 雨季, 梅雨, 秋雨 )