If you’re traveling to Japan in the summer months, you might experience an intense downpour that comes out of nowhere—flooding streets, stopping trains, and soaking everything in sight. These sudden and powerful storms are known in Japan as “guerrilla rainstorms” (ゲリラ豪雨), and they’re becoming increasingly common.
Here’s what you need to know as a visitor: what guerrilla rainstorms are, why they happen, and how to stay safe when they strike.
🌧 What Is a Guerrilla Rainstorm?
A guerrilla rainstorm is a short but extremely intense downpour, often accompanied by thunder, strong winds, and even hail. Unlike regular rain, these storms:
- Happen suddenly, often without warning
- Are very localized (one city district may be dry while another floods)
- Typically last 30 to 60 minutes, but cause major disruption
🗾 Why Are They So Common in Japan?
Japan’s hot and humid summers create the perfect conditions:
- High temperatures + high humidity = strong rising air currents
- When warm air meets cooler air layers, thunderclouds rapidly form
- These clouds release intense rainfall in a very short time
⚠️ Real-World Examples
- Tokyo (June 2024): A guerrilla storm dropped over 80mm of rain in 30 minutes near Shinjuku Station. Underground passageways flooded, and several subway lines stopped service.
- Kyoto (August 2023): A sudden storm flooded historic streets in Gion. Tourists in yukatas were caught without shelter or umbrellas, leading to confusion and minor injuries from slipping.
🧭 Key Risks for Tourists
- Flooded streets and underpasses
→ Avoid walking through low-lying roads, underpasses, or subway entrances during heavy rain. - Public transportation delays
→ Trains and buses may be delayed or suspended without warning. - Sudden power outages
→ Be prepared for potential blackouts, especially in rural areas. - Language barriers in emergency situations
→ It can be harder to understand local alerts if you don’t speak Japanese.
✅ What Tourists Should Do: Practical Tips
1. Check the Weather Every Morning
Use apps with radar and rain alerts:
- “Safety Tips” app (by Japan Tourism Agency, English supported)
- Yahoo! Weather Japan (with “rain cloud radar”)
- Google Weather also gives storm warnings
2. Pack a Compact Umbrella or Rain Poncho
- Tip: Local stores like Daiso or Don Quijote sell lightweight ponchos and umbrellas for under ¥500.
3. Avoid Underground Facilities During Heavy Rain
- Example: Don’t use underground malls or pedestrian tunnels if heavy rain begins—they flood quickly.
4. Identify Safe Shelters in Advance
- Look for:
- Convenience stores (e.g. 7-Eleven, Lawson)
- Train stations
- Shopping malls or hotel lobbies
These places often stay open and dry during storms.
5. Don’t Take Lightning or Wind Lightly
- If you hear thunder, immediately seek shelter indoors.
- Avoid riversides, open parks, and temple gardens until the storm passes.
6. Prepare a Mini Emergency Kit
Include:
- Water bottle
- Portable phone charger
- Towel or cloth
- Basic medications (for motion sickness, headaches)
- Japanese emergency phrases printed out or saved on your phone
🌈 Bonus Tip: How Locals React
- Most Japanese people treat guerrilla storms as normal and will immediately seek cover when the sky darkens.
- When you see people suddenly opening umbrellas or rushing into shops—it’s a sign to do the same!
📝 In Summary
| Danger | Your Action |
|---|---|
| Sudden rain | Carry a compact umbrella or poncho |
| Flash flooding | Stay above ground, avoid underpasses |
| Train delays | Check live updates on transit apps |
| No English alerts | Use “Safety Tips” app for English notifications |
| Stuck in the rain | Find shelter in convenience stores or stations |
🧳 Enjoy Japan, Rain or Shine
Guerrilla rainstorms may seem scary, but they’re manageable with the right information and awareness. By planning ahead and staying alert, you can enjoy Japan’s summer festivals, temples, and nightlife safely—even if the skies open up unexpectedly.
So pack your umbrella, stay connected, and don’t let a little rain wash away your adventure!