In Japan the tsuyu, or “rainy season,” starts in early June and lasts for about a month. During this period, the seasonal rain front remains stationary over the Japanese archipelago and normally causes prolonged precipitation. Heavy rains often result in mudslides and flooding, and the extremely high humidity is not only unpleasant but also increases the risk of food poisoning. Still, this rainy season is indispensable for the life of the Japanese people. If there is not enough rain at this time of year, there is a significant impact on crops and water resources. 意訳：６月から７月上旬に掛けて，日本列島に前線が停滞し長雨が続く現象．梅雨の時期は土砂崩れや水害が発生し，湿度も上がるため食中毒の危険性も高まる．しかし，この時期にある程度まとまった雨が降らないと飲料水や農作物に多大な影響が出る
The rainy season 「has set in [is over].
The length of this year's rainy season broke all records.
梅雨明けthe end of the rainy season
梅雨入りthe beginning of the rainy season
The rainy season was officially declared to have begun in the Kyushyu district.