Japan’s rainy season—known as tsuyu or baiu—is a unique early-summer period marked by steady rain, warm humidity, and the soft, muted beauty of hydrangeas. More than just a weather pattern, tsuyu subtly influences daily life, travel plans, and the overall atmosphere of June and early July in Japan. What Is Tsuyu? Tsuyu is Japan’s annual rainy season. A slow-moving seasonal rain front settles over the archipelago, creating weeks of drizzle, cloud cover, and humid air. The term tsuyu literally means “plum rain,” as this period coincides with the ripening of plums (ume) across Japan. When Does the Rainy Season ...