June is the wettest month of the year across Honshu, with tropical showers occurring until early July. In terms of temperature and weather conditions, spring and autumn are typically the most pleasant times of the year to visit Honshu.

While many people think of June as the wettest because of the Tsuyu (rainy season), September is statistically the wettest month for much of Japan, including Tokyo and Osaka. This is primarily due to the peak of the typhoon season. While the June rainy season brings persistent drizzle and overcast skies, September's rainfall is often much more intense, delivered in heavy downpours as tropical storms move across the archipelago. On average, Tokyo receives around 210mm of rain in September, compared to roughly 165mm in June. However, geography plays a huge role; in the southern islands of Okinawa, the rainy season starts much earlier (May), and the heaviest rain is usually then. If you are planning a trip to Japan, October and November are generally the driest and most popular months for sightseeing, while the summer months of June through September are the most unpredictable for those who want to avoid the rain and high humidity.