This week, the 気象庁 (Kishōchō, Meteorological Agency) announced rainy season had “likely” begun in the Kanto-Koshin and Hokuriku regions, with areas south of that entering the period known as 梅雨 (tsuyu, rainy season) days prior.
The word 梅雨 is made up of two kanji: 梅 (ume, plum) and 雨 (ame, rain).
The latter kanji, 雨, is an obvious choice. Look out your window for most of June and you’ll see a lot of rain.