Voyafield · Articles · 2026-06-07 · English
Japan's Rainy Season: When Is Tsuyu, and How Wet Does Japan Really Get?
A six-city data look at the season known as tsuyu — rain, humidity, and what it means for travel
If you're planning a trip to Japan in late spring or early summer, one word keeps showing up: tsuyu (梅雨). It's the rainy season — a roughly month-long stretch when a warm, wet front parks over the archipelago and the umbrella stays close.
But "Japan is rainy in June" is too coarse a statement to plan around. Tsuyu doesn't hit the whole country at the same time, and it doesn't hit every region with the same force. The Voyafield weather record covers daily observations for every prefecture; this article pulls out what last year's tsuyu actually looked like in six cities travelers care about — Tokyo, Kyoto, Osaka, Fukuoka, Sapporo (Hokkaido), and Naha (Okinawa) — by rainfall, temperature, humidity, and cloud cover.
1. When does tsuyu actually arrive?
The rough JMA convention, year to year:
- Okinawa: tsuyu typically begins in early May and lifts in mid- to late June. The rainy season here arrives earlier and finishes earlier than on the main islands.
- Mainland Japan (Kyushu, Shikoku, Honshu): tsuyu generally begins in early to mid-June and ends in mid- to late July. Kyushu enters first; the Kanto plain (Tokyo) typically a few days behind.
- Hokkaido: by JMA convention, Hokkaido does not have a declared tsuyu season — JMA's regional list of tsuyu declarations runs from Okinawa up to northern Tohoku and does not include Hokkaido. As the data below shows, that doesn't mean Hokkaido is dry in June; it does not usually show the official tsuyu pattern used for regions farther south.
2. How wet did last year's tsuyu actually get?
Total monthly rainfall through May, June and July 2025 — the bold cell in each row is the natural rainy-season month for that region.
| Prefecture (Voyafield observation point) | May 2025 | June 2025 | July 2025 |
|---|---|---|---|
| Hokkaido (Sapporo) | 76 mm | 187 mm | 218 mm |
| Tokyo | 203 mm | 478 mm | 146 mm |
| Kyoto | 73 mm | 564 mm | 166 mm |
| Osaka | 124 mm | 546 mm | 199 mm |
| Fukuoka | 12 mm | 665 mm* | 104 mm |
| Okinawa (Naha) | 99 mm | 80 mm | 185 mm |
A few patterns stand out:
- Kyushu and Kansai took the worst of it. Fukuoka went from a near-empty 12 mm in May to a Voyafield-recorded 665 mm in June — a classic tsuyu signature — then dried out to 104 mm by July. Kyoto and Osaka followed the same shape, clearing 540 mm in June from light Mays.
- Tokyo's tsuyu started early. May 2025 already saw 203 mm of rain there — consistent with JMA's finalized dates putting many mainland regions into tsuyu unusually early in 2025 — before June added another 478 mm and July dropped to 146 mm.
- The southern and northern extremes look different. Okinawa had its wettest month in May (99 mm) and was already winding down by June (80 mm) — 2025 was a quiet tsuyu year for it. Sapporo, meanwhile, shows a gentle 76 → 187 → 218 mm climb without the sharp June spike-and-drop that defines tsuyu farther south.
3. The muggy factor: humidity and cloud cover
Rainfall totals tell you whether to pack a jacket. Humidity tells you whether you'll be comfortable inside it. Voyafield records mid-afternoon humidity and cloud cover daily; here are the June 2025 averages for the same six cities.
| Prefecture | Afternoon humidity | Afternoon cloud cover |
|---|---|---|
| Hokkaido (Sapporo) | 67 % | 63 % |
| Tokyo | 62 % | 63 % |
| Kyoto | 64 % | 76 % |
| Osaka | 61 % | 58 % |
| Fukuoka | 66 % | 57 % |
| Okinawa (Naha) | 78 % | 60 % |
Two things to take from this. First, these are afternoon readings, when temperature peaks and relative humidity is at its daily low — morning humidity is typically higher, but Voyafield's dataset only stores the afternoon value. Second, Kyoto's 76 % cloud cover stands out — a grey-sky tsuyu month that matches the city's reputation — while Okinawa stayed at 78 % humidity in June even after the rain had moved on. Across all six cities, the air often feels warmer, heavier, and more humid than the temperature alone suggests.
4. Putting rain in perspective for travelers
Even at Fukuoka's tsuyu peak — 665 mm in a month — that averages to about 22 mm per day. In practice, tsuyu rain doesn't fall as a constant drizzle; it tends to arrive as a handful of genuinely wet days clustered with cloudy-but-dry stretches. So a one-week visit to Kansai in late June will see some heavy rain, almost certainly, but not seven straight days of it.
A few practical takeaways:
Where to lean for less rain. Hokkaido is the clear June choice — Sapporo's rainfall is meaningful but doesn't come with the tsuyu humidity spike, and afternoons are cooler (around 25 °C against Osaka's 29 °C). Okinawa works too, but only after mid-June, once its own rainy season has wound down.
Where to expect the wettest experience. Kyushu (Fukuoka) and Kansai (Kyoto, Osaka) in June, in that order. Temple gardens in light rain are genuinely beautiful; folding umbrellas are easy to buy at any convenience store for a few hundred yen, so packing one is optional.
The quieter side. Late June into the first week of July sits between two of Japan's busiest travel windows — Golden Week (early May) and the summer break (mid-July onward). For some travelers, this stretch can feel calmer than those peaks.
5. What's in season while it rains
The tsuyu front and the calendar happen to line up with several seasonal phenomena across Japan — things that depend on this specific mix of warmth, moisture, and timing rather than on any tourist schedule.
- Hydrangeas (ajisai, 紫陽花) peak in mid-June across much of Honshu. Commonly cited viewing spots include Meigetsu-in and Hase-dera in Kamakura, and Mimuroto-ji in Uji south of Kyoto. The blooms shift color depending on soil acidity, and the rain itself is part of the visual story.
- Japanese irises (hanashobu, 花菖蒲) peak slightly earlier — late May into early June — at gardens such as Horikiri Shobuen in Tokyo.
- Fireflies (hotaru, 蛍) appear from mid-June along clear streams, mostly in rural Honshu and northern Kyoto. Their season is short — roughly two to three weeks — and overlaps almost exactly with peak tsuyu.
These aren't tourist attractions in the conventional sense — they're seasonal events that travelers happen to be able to see if their dates line up.
6. Caveats worth keeping
- One year is one year. 2025 itself was an unusual cycle: JMA's finalized dates show many mainland regions entered tsuyu unusually early and exited by late June, so the July column above reads as a post-tsuyu comparison month rather than as pure rainy-season data. Other years will look different.
- Specific tsuyu dates aren't in this dataset. JMA publishes them each year; if exact dates matter for your trip, check 気象庁 (jma.go.jp) directly.
This article is written by an independent developer who has lived in Japan for a long time. Voyafield (voyafield.com) is built and maintained by the same person, who pulls and curates the data from public sources. Weather figures here come from Voyafield's prefecture-level daily precipitation, temperature, humidity and cloud cover record; tsuyu timing conventions follow JMA's standard description but specific year-by-year dates are not stored in this dataset.