Why these months specifically
June: Rainy season starts (tsuyu)
The rainy season runs from early June to mid-July across most of Honshu. Expect 170mm of rain in June (vs. 50mm in December). It rarely rains all day — typical pattern is heavy bursts followed by humid sun. Hokkaido is the exception: it skips tsuyu entirely and is excellent now.
July: Tsuyu ends, then peak heat
Mid-July the rains end and Tokyo's heat takes over. Average highs hit 30°C with humidity that makes it feel like 35°C. Gion Matsuri in Kyoto (July 17) is a major draw despite the weather — Kyoto in mid-July is fascinating but exhausting.
August: Hottest month + Obon
August averages 31°C in Tokyo with regular spikes above 35°C. Obon (August 13-15) is the year's second domestic travel rush — book trains and accommodation 4+ months ahead or avoid these dates. Hokkaido stays 5-8°C cooler.
September: Typhoon season peak
September has the year's highest rainfall (220mm) and highest typhoon frequency. Late September can be wonderful if you dodge storms — autumn colors begin in the north. But build in flexibility: typhoons routinely shut down trains and flights for 1-3 days.
What to do instead
If you must travel during summer:
- Hokkaido skips the rainy season entirely. Lavender at Furano (July), hiking in Daisetsuzan, cool nights in Sapporo — Japan's summer escape.
- Japanese Alps (Kamikochi, Kiso Valley, Hakuba) stay 5-10°C cooler than Tokyo and offer alpine hiking.
- Festival-focused trips — if you specifically want Gion Matsuri or Tenjin Matsuri, the timing constraint is non-negotiable. Plan for the festival, accept the heat.
The flip side: when to actually go
Late March to early May, or October to November. Both are described as Japan's two great windows for travel. See the full Japan seasonality map for month-by-month detail.