Record rainfall kills eight in Japan's Chiba, thousands stranded at Narita airport

Casualties and damage

At least eight people have died in Chiba prefecture east of Tokyo after torrential rains struck eastern Japan on Thursday 13 August and into Friday morning. The death toll rose through the day: Reuters reported four deaths early Friday, the provincial government later raised the figure to five, and by Friday NHK reported at least eight dead. Victims include a 66-year-old woman trapped in her submerged vehicle and a man whose body was found on a flooded road. Another victim collapsed in the street and died after being rushed to hospital. Authorities reported more than 30 injured. In rural areas of Chiba, dozens of cars were abandoned on mud-covered roads, while emergency teams worked through Friday to clear and repair damaged sections. Soldiers were dispatched to assist with relief operations.

Record rainfall and alerts

More than 360 millimetres of rain fell in 24 hours in parts of Chiba prefecture. In the Chuo district of Chiba city, 115 millimetres fell in a single hour, roughly the normal rainfall for the entire month of August. Sakura recorded 189.5 millimetres in three hours, a new record. Chiba recorded over 100 millimetres per hour since Thursday afternoon, about three times the average August rainfall and the highest volume ever recorded in the country. The Japan Meteorological Agency issued a Level 5 alert, the highest level, for more than a third of municipalities in Chiba, the first such alert for rain in the prefecture and the first since new disaster weather services were introduced in May. The alert was downgraded to Level 4 on Friday morning, though landslide and flood risks persisted.

This case was an extremely unusual situation, even by Japan's historical weather standards. I have responded to many disasters in the past, but I have never experienced a case like this.

Transport chaos at Narita

Around 7,000 travellers were stranded overnight at Narita airport, one of Tokyo's two main international hubs, after flooding disrupted rail and road connections. Fanpage reported approximately 6,000 stranded. Airport staff distributed sleeping bags, water and snacks to passengers who spent the night in the terminals. A spokesperson said all flights were expected to operate normally on Friday, though Japan Airlines warned that some flights could experience delays. Several rail services remained suspended on Friday morning, though some trains connecting Narita to Tokyo had resumed. Highways in Chiba, including routes linking the airport to central Tokyo, remained closed, causing heavy traffic. Hundreds were also stranded at Chiba railway station.

Power, gas and evacuations

Flooding at an electrical substation left more than 20,000 households without power in the early hours of Friday, according to Tokyo Electric Power. Gas supply to nearly 13,000 homes was temporarily interrupted. Over 100,000 families had been asked to evacuate their homes after the rain triggered landslides and power outages. Hundreds of residents spent the night in shelters set up in schools, gymnasiums and other public buildings. The disaster struck during one of Japan's busiest holiday weeks, the Obon festival, when millions travel to visit family graves and ancestral homes.

Weather causes and ongoing risk

The Japan Meteorological Agency attributed the extreme rainfall to warm, humid air from the east meeting cold air in higher atmospheric layers, creating highly unstable conditions. Asahi Shimbun reported that the downpours could not be predicted by the warning system due to a "linear precipitation band", where lines of clouds form in a restricted area and trigger torrential rain for hours. River engineering specialist Koji Ikeuchi, cited by Nihon Keizai Shimbun, noted that urban areas covered with asphalt and concrete prevent water from draining, promoting accumulation in low-lying zones. The agency warned that heavy rain could continue in Chiba and surrounding areas until Saturday. The flooding followed storms and typhoons named Dolphin, Chan-hom and Peilou that swept across Japan and neighbouring countries this week.