On July 17, 2026, Tochigi and Gunma prefectures experienced record-breaking rainfall that triggered widespread evacuation orders and emergency alerts, affecting hundreds of thousands of residents including foreign nationals living in these areas. Understanding Japan's disaster warning system and knowing how to respond could be lifesaving for expats residing in or near affected regions. According to NHK, the severe weather began on the evening of July 17 when moist air caused continuous rain clouds to develop over both prefectures, resulting in record precipitation levels. The Japan Meteorological Agency issued a "linear precipitation band imminent forecast" at 9:48 PM, warning that a dangerous weather phenomenon was developing. Linear precipitation bands occur when developed rain clouds align in a row, producing intense rainfall over the same area for extended periods, significantly increasing flood and landslide risks. The rainfall intensity was extraordinary. In Ota City, Gunma Prefecture, radar analysis detected approximately 100 millimeters of rain in just one hour around 5:30 PM, prompting the Meteorological Agency to issue a "record short-term heavy rain" emergency alert. This level of precipitation overwhelms drainage systems and creates immediate disaster risks. Multiple municipalities responded by issuing evacuation orders affecting vast populations. Ashikaga City in Tochigi Prefecture issued evacuation orders for 89,572 people across 45,459 households at 10:50 PM on July 17, following Level 4 heavy rain and landslide warnings. The situation escalated further when the Hatakawa River threatened to overflow. At 12:30 AM on July 18, authorities upgraded warnings to "Emergency Safety Assurance" (Level 5, the highest alert level) for 17,812 residents in the Keno and Tomita districts. Sano City in Tochigi Prefecture also experienced critical conditions. After the Hatakawa River actually overflowed, authorities issued Emergency Safety Assurance orders for 6,520 people in 2,249 households near the river. Additionally, approximately 9,000 residents in western Sano received evacuation orders at 10:15 PM. In Gunma Prefecture, the Ishida River, part of the Tone River system in Ota City, received a Level 4 flood danger warning at 12:20 AM. Multiple cities including Maebashi, Isesaki, Kiryu, and Midori received heavy rain warnings, while landslide warnings were issued for areas including Maebashi City. For foreign residents, understanding Japan's five-level disaster warning system is crucial. Level 3 means elderly and vulnerable people should evacuate. Level 4 requires all residents in affected areas to evacuate immediately. Level 5, "Emergency Safety Assurance," means disaster is occurring or imminent—residents should take immediate action to protect their lives, whether by moving to higher floors or the nearest safe location, as evacuation routes may already be dangerous. The damage was significant, with reports of flooding and landslides throughout both prefectures. A landslide occurred in Ashikaga, while Gunma authorities received numerous flood reports. By the morning of July 18, some warnings were downgraded—Sano City's landslide warning was reduced to advisory level at 4:01 AM, and Ashikaga's at 5:01 AM—but residents were warned that thunderstorms could continue affecting northern and western Japan. Expats should ensure they have emergency alert apps installed on their phones, including NHK World for English-language updates and their municipality's official disaster notification system. Understanding local evacuation routes and designated shelters before emergencies occur is essential. Keep emergency supplies ready, including water, food, flashlights, and important documents in waterproof containers. This event demonstrates that Japan's summer rainy season can produce life-threatening conditions with little warning. Foreign residents should take all evacuation orders seriously and act immediately when authorities issue warnings.