Japan’s typhoon season runs from June through October, peaking in August and September. Typhoons (台風, taifū) bring sustained high winds, torrential rain, storm surges, and flooding. For residents, understanding the warning system and preparing in advance makes the difference between a disrupted week and a dangerous situation.
Japan’s Weather Warning System
The Japan Meteorological Agency (JMA) issues a tiered warning system that escalates as storms approach:
- Advisory (注意報) — elevated caution, prepare provisions, check plans
- Warning (警報) — significant danger; outdoor activities should stop, vulnerable structures at risk
- Special Warning (特別警報) — rare, catastrophic risk; immediate action required
The JMA website and app (気象庁) provides real-time tracking, rainfall warnings, and river flood alerts. NHK World broadcasts English-language typhoon updates. Windy.com and Weather Underground are useful English-language tools for tracking typhoon paths.
Tracking Typhoon Paths
Japanese weather services publish typhoon path forecasts (予報円, forecast cone) showing probable track for the next 72–120 hours. The cone widens with time — a typhoon 5 days out could shift considerably. Track updates every 3–6 hours as a typhoon approaches. Typhoon paths typically enter Japan from the south or southeast, traverse the main islands, and exit into the Pacific or Sea of Japan. The Kanto region (Tokyo area) is commonly affected in September.
Pre-Typhoon Preparation (1–2 Days Before)
When a significant typhoon is forecast to pass near your area, take these steps:
- Water supply: Fill bathtubs, large pots, and portable containers — water outages can follow flooding
- Food: Stock 3+ days of non-cooking food; convenience stores sell out 24–48 hours before landfall
- Power bank: Fully charge all portable batteries and devices
- Cash: Withdraw cash — ATMs and card readers may be offline during outages
- Outdoor items: Bring in bicycles, potted plants, drying racks, anything the wind can turn into a projectile
- Windows: Do not tape X patterns on windows — this does not prevent shattering and is dangerous. Close all shutters (雨戸). If you have no shutters, move away from windows during peak winds
- Drains: Clear gutters and outdoor drains of leaves and debris
During a Typhoon
Stay indoors during peak winds. If your building shakes, move to an interior room away from windows. Do not go outside during apparent calm — the eye of a typhoon passing overhead creates a brief lull before the back wall arrives with equal or greater force. Japanese TV will broadcast real-time information on the eye’s position.
Avoid rivers, canals, and drainage channels during and after heavy rain — water levels rise rapidly and river banks become extremely dangerous. Level 5 (緊急安全確保) and Level 4 (避難指示) evacuation orders should be followed immediately, especially if you live near rivers, steep slopes, or low-lying areas.
Japan’s 5-Level Evacuation Warning System
- Level 1 — Disaster awareness (災害への心構え)
- Level 2 — High-risk elderly/disabled should evacuate (高齢者等避難)
- Level 3 — Evacuation order for high-risk individuals (高齢者等避難)
- Level 4 — All residents should evacuate (避難指示)
- Level 5 — Already in disaster; take life-saving action now (緊急安全確保)
Alerts are sent via J-Alert to all phones in the affected area and broadcast on TV. Level 4 and 5 require immediate action — do not wait to see how bad conditions get.
Flood, Landslide, and River Overflow Risk
Heavy typhoon rainfall causes flooding, landslides (土砂災害), and river overflow. Your municipal hazard map shows landslide risk zones (土砂災害警戒区域) and flood inundation zones. If you live in a marked area, act early — do not wait until Level 4. River overflow tends to happen 6–12 hours after peak rainfall as water flows downstream. The River Flood Risk Line (川の防災情報, mlit.go.jp) tracks river water levels in real time.
After the Typhoon
Avoid flooded roads and rivers for 24–48 hours after the storm — contaminated water, hidden debris, and weakened structures make post-typhoon exploration dangerous. Downed power lines may be submerged in flood water. Report structural damage to your building manager or ward office. If you lose power, report to TEPCO (Tokyo area: 0120-995-007) or your regional power company.
Key Resources
- JMA Typhoon Information (jma.go.jp/en) — official English-language forecasts
- NHK World — live English typhoon broadcasts
- Safety Tips app — multilingual evacuation alerts
- River Flood Risk Line (mlit.go.jp) — river levels by location
- Your municipal hazard map — flood, landslide, and shelter information