A wall of record-breaking rain has turned roads into rivers east of Tokyo, killing at least six people and leaving more than 10,000 travellers and commuters stranded across Japan’s Chiba prefecture.Around 7000 people were forced to sleep inside terminals at Tokyo’s Narita International Airport after floodwaters severed rail and road connections during one of Japan’s busiest holiday travel periods.Emergency workers could be seen handing out sleeping bags, water and food as families bedded down across crowded departure halls on Thursday night.The worsening toll emerged on Friday morning, with figures compiled by Chiba prefectural and city authorities showing six people had died. Another person was in cardiac arrest and one remained missing.Among the victims was a man believed to be in his 60s or 70s who was found floating on a flooded road in Ichikawa.A 66-year-old woman also died after becoming trapped inside her submerged car in Sakura, while other victims were found in flooded vehicles or collapsed on streets across the prefecture.The scale of the downpour was extraordinary even by the standards of disaster-prone Japan, with over 360mm of rain falling within 24 hours in parts of Chiba.Chiba city recorded 115mm in a single hour on Thursday evening, followed by 188.5mm over three hours and 293mm in six hours. All three totals smashed local records dating back to 1966.“This case was an extremely unusual situation, even by Japan’s historical weather standards,” Chiba Governor Toshihito Kumagai said.“I have responded to many disasters in the past, but I have never experienced a case like this.”Almost 230,000 residents were urged to seek safer ground as floodwaters poured through streets, swallowed cars and entered homes.An early damage count found more than 80 homes had been flooded, but authorities warned the true figure was likely to rise as emergency crews reached more of the affected areas.The rain knocked out power to about 68,000 households at its peak. Roughly 23,000 remained without electricity on Friday morning.Japan’s Meteorological Agency issued its highest Level 5 heavy rain warning across 22 Chiba municipalities as the deluge intensified, along with its most severe landslide warning in six areas.Those warnings were downgraded to Level 4 shortly after 5am on Friday as the worst of the rain eased.However, forecasters warned that the atmosphere remained highly unstable and further intense thunderstorms were possible later in the day. Waterlogged ground and swollen waterways also meant even comparatively modest rainfall could trigger fresh flooding or landslides.At Narita, the airport company said approximately 7000 people remained inside the terminals at 4am after buses and trains linking the airport with central Tokyo were suspended.“I never thought I’d spend the night at the airport, but it is what it is and we are learning,” one stranded traveller told Japanese broadcaster NHK.“We’re never going to forget this trip.”Rail links began reopening in stages on Friday morning, although delays, cancellations and long queues continued.Flights were operating broadly as scheduled, with Japan Airlines warning that some services could be delayed but saying no widespread cancellations were expected.The chaos extended far beyond the airport.More than 4000 people spent the night inside JR Soga station after surrounding streets were submerged by water that reached as high as an adult’s waist.As many as 1700 other people took shelter inside the Chiba prefectural government building and a neighbouring government facility, while 11 temporary accommodation sites were opened across Chiba city.Dozens of abandoned vehicles remained scattered across flooded roads on Friday morning. On one stretch of road in central Chiba, more than 20 vehicles blocked traffic across approximately 150 metres.Major highways linking Narita Airport with Tokyo were also closed or heavily congested, forcing motorists onto alternative routes.Weather experts said the disaster was caused by a rare combination of cold air high in the atmosphere, an enormous supply of warm, moist air and converging winds over Chiba.