Yakushima in Rainy Season: Why June and July Are the Best Months to Visit Japan's Ancient Forest
There's a saying on Yakushima: "It rains 35 days a month." It's a joke, but barely. The island receives between 4,000 and 10,000mm of rainfall annually — the most of any place in Japan — and the mountain interior can see rain on 300+ days per year.
Most travel advice says avoid tsuyu (rainy season, June-July). I'd say the opposite: tsuyu is when Yakushima becomes the island that inspired Princess Mononoke.
The Rain as Feature, Not Bug
Yakushima's ancient cedar forests are moss forests. Moss requires moisture. In dry weather, the moss is muted green, compact, clinging to the bark. In rain, it swells — becoming luminous, dripping, covering every surface in a thick velvet that transforms the forest into something from a Miyazaki film.
The Shiratani Unsuikyo Ravine — the actual forest that Studio Ghibli used as reference for Princess Mononoke — is spectacular in any season. In the rain, with mist threading through the cedars and moss glowing emerald on every rock and root, it becomes transcendent.
I'm not being hyperbolic. I've been to Yakushima twice — once in October (dry-ish), once in June (tsuyu). The June visit was immeasurably more beautiful.
What the Rain Actually Looks Like
Tsuyu rain on Yakushima isn't a constant downpour. The pattern varies:
Light drizzle (40% of rainy days): A fine mist that barely requires an umbrella. The forest steams. Visibility is atmospheric.
Steady rain (40%): Proper rain that requires waterproofs. The trails get slippery. Waterfalls swell. Rivers rise.
Heavy downpour (20%): Real rain. Trails can become streams. Mountain trails may close temporarily. This is the day to visit the coast, the onsen, or the museum.
Rain typically comes in cycles — 3-4 hours of rain, 1-2 hours of clearing, repeat. You can absolutely hike between rain bands.
The Jomon Sugi Trek in Rain
The flagship hike — 22km round trip to the Jomon Sugi, a cedar estimated at 2,200-7,200 years old (the range is that wide because nobody can core-sample a national treasure). In dry weather, this is a long, hard hike. In rain, it's a long, hard, magical hike.
The first 8km follow an old logging railway — flat, easy, beautifully atmospheric in mist. The remaining 2.5km climb steeply through the forest to the viewing platform.
In tsuyu:
The railway trail has streams of rainwater running along the rails — you walk through a moving waterscape
Waterfalls along the trail are at full power — Oogata Waterfall and Kosugi-dani Cedar (another ancient tree, 3,000+ years) are framed by cascading water
The Jomon Sugi itself, in mist, looks like a being rather than a tree. The trunk (16.4m circumference) disappears into the fog above.
Practical notes: Start at 5AM from the Arakawa trailhead (entry by bus only, JPY 1,400 round trip, reservation required). The hike takes 8-11 hours. Bring 2L of water, lunch, rain gear, and headlamp (in case you return after dark).
Waterfalls at Peak Flow
Oko-no-Taki — Yakushima's tallest waterfall (88m). In dry season, it's a thin cascade. In tsuyu, it's a thundering column of water with spray that reaches the viewing platform 100m away. Free. 30-minute drive from Miyanoura port, then a 30-minute walk.
Toroki-no-Taki — One of the few waterfalls in Japan that flows directly into the ocean. In tsuyu, the volume doubles and the freshwater river meets the sea in a turbulent collision. Short walk from the road. Free.
Senpiro-no-Taki — A 60m cascade in a granite gorge. The swimming pool at the base is accessible in dry season but dangerous in heavy rain. Go for the view, not the swim, in June-July.
Shiratani Unsuikyo: The Mononoke Forest
Entry: JPY 500 (conservation fee). Three trail options: 1 hour, 3 hours, or 5 hours. The 3-hour loop is ideal — it covers the Mononoke-hime no Mori (Princess Mononoke Forest) section where the moss is thickest and the cedars are oldest.
In tsuyu, the forest floor is covered in luminous moss, the air is thick with moisture, and the light filtering through the canopy creates the exact atmosphere that Miyazaki captured in the film. I met a Japanese couple on the trail who were crying. They'd grown up watching Princess Mononoke and this was their first visit.
Accommodation in Rainy Season
Lower demand means easier bookings and sometimes lower prices.
Yakushima South Village — Hostel-style, dorms from JPY 3,500/night, communal kitchen
Minshuku Soyotei — Traditional guesthouse, JPY 8,000/night with dinner
Sankara Hotel — The luxury option, JPY 35,000-80,000/night, onsen, restaurant
After a rainy hike, an onsen (hot spring bath) is essential. Hirauchi Kaichu Onsen — a natural hot spring on the coast that's only accessible at low tide — costs JPY 200 and the experience of soaking in volcanic-heated water while rain falls on your head and the Pacific crashes on the rocks beside you is unrepeatable.
Packing for Tsuyu
Rain jacket: Hardshell, not softshell. You need waterproof, not water-resistant.
Rain pants: Non-negotiable. Your legs will be wetter than your torso.
Waterproof boots: Trail runners are fine in dry season. Rain demands waterproof hiking boots with grip.
Pack cover + dry bags: For electronics, extra clothes, and lunch.
Gaiters: For the Jomon Sugi trail, which becomes a stream in heavy rain.
Quick-dry towel: For wiping camera lenses, glasses, and your face every 5 minutes.
The Sound
This is the detail nobody writes about. Yakushima in the rain has a sound that doesn't exist anywhere else I've been — rain on ancient cedar bark, rain on thick moss, rain on ferns, rain on granite, rain on the surface of mountain streams. It's layered. Each surface produces a different frequency. The forest hums.
You can't record it adequately. You can't photograph it. You can only stand in it and let your nervous system process something primal.
That's the argument for tsuyu. Not despite the rain. Because of it.
