Tokyo’s rainy season (梅雨, tsuyu) runs June–July and creates the most significant hair management challenge of the year for most expats. Here’s what I’ve seen actually work — across 23 years and thousands of clients in this specific climate.
Why Rainy Season Is Different From Other Humidity
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📍 Ginza / Yokohama · English · 中文 · 23 years
The challenge of Tokyo’s rainy season isn’t just high humidity — it’s the combination of sustained high humidity (80–90%) with the seasonal shift from spring’s relatively dry conditions. Hair that adapted to spring behaves differently in June’s sustained moisture. The shift happens quickly, and most clients notice it within the first week of rainy season.
Before Rainy Season: What to Do Now
April–May: The best time for straightening
If you’re considering acid straightening, April–May is the ideal window. The treatment takes 3–5 hours and the bond restructuring stabilises over 48 hours. Getting it done before rainy season means you go into June with fully stabilised results, and you experience the benefit immediately when humidity arrives. Appointments in April–May fill faster than any other time of year.
Switch your shampoo before June
Switching to a silicone-free shampoo 4–6 weeks before rainy season allows the buildup removal process to complete before humidity peaks. Clients who switch in April typically notice a meaningful difference in how their hair responds in June compared to the previous year.
During Rainy Season: Daily Survival
- Never air dry — always blowdry completely before going outside. Air drying in June’s humidity sets the cuticle in a lifted, frizzy state
- Concentrator nozzle, downward direction — smooths the cuticle as you dry
- Cool shot to finish — closes the cuticle before you go outside
- Lightweight oil on damp hair — 2–3 drops of a non-silicone oil before the final blowdry pass
- Always carry an umbrella — the simplest intervention, consistently effective
The Structural Solution: Acid Straightening
For expats who find rainy season genuinely affecting quality of life, Japanese acid straightening is the only structural solution. Surface products manage humidity reactivity; acid straightening reduces it at the bond level. Clients who have the treatment consistently describe the following rainy season as a fundamentally different experience. Is it worth it for you? →
SBCP Raw Mineral Shampoo
Switch before rainy season · silicone-free · Japan-formulated
📍 KENJI HAIR LOUNGE — GINZA & YOKOHAMA
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English · 中文 · 日本語 · One-on-one · 23 years · Singapore experience
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