Right now, most of Japan is right in the middle of the rainy season, but the exact period varies from a province to another. The rainy season, tsuyu ("plum rain", named like that because it takes place when the plum fruits start to ripen), begins after the first week of May in Okinawa (approx between May 8 and June 23), after the first week of June in Kansai and Kanto (June 6-8 to July 20) and it is almost non-existent in Hokkaido.
When you program your trip in Japan, keep in mind the rainy season. You won’t loose much by avoiding it, because most of the important events or festivals in Japan are also scheduled to avoid the rain. And if you like taking photos in the rain (as I do), you’ll have lots of chances anyway, because there are quite a few precipitations during spring, summer and fall too, sometimes even torrential rainfalls, like when I took this photo in the Kichijoji Station from Tokyo…
Yesterday’s Japan Photo: