Torrential rain described by officials as unprecedented struck Chiba prefecture, just east of Tokyo, on 13 and 14 August 2026, leaving several people dead, cutting power to tens of thousands of households and stranding roughly 7,000 travellers overnight at Narita Airport. Japanese public broadcaster NHK, the Kyodo news agency and the Asahi newspaper initially reported six deaths and five injuries, though later reporting on the same storm system has put the confirmed toll at four dead, with at least one other account citing five dead and one person still missing.
Local authorities issued a level-five emergency warning, the highest alert available, on Thursday, 13 August. It was downgraded to level four by Friday morning, though officials continued to warn residents of ongoing landslide and flooding risks.
What caused the record rainfall?
Japan's Meteorological Agency attributed the deluge to warm, moisture-laden air moving into eastern Japan and colliding with colder air aloft, creating highly unstable atmospheric conditions. According to a report from Chosun Biz, the agency specifically linked the heaviest rain to Typhoon No. 15, known as Chan-hom, which had weakened into a tropical depression but left abundant moisture hanging over Chiba. The bureau separately called the event an "unprecedented level of heavy rain."
Chiba Governor Toshihito Kumagai told reporters on Friday morning that the scale of the event was without precedent in his experience.
"This case was an extremely unusual situation, even by Japan's historical weather standards," Chiba Governor Toshihito Kumagai told reporters on Friday morning. "I have responded to many disasters in the past, but I have never experienced a case like this."
Officials said Chiba logged more than 100mm of rainfall per hour from Thursday afternoon onward, roughly three times the region's typical rainfall for the entire month of August, and the highest hourly volume of precipitation ever recorded in Japan. According to the Japan Times, one weather station in Midori Ward recorded about 450mm of rain within a six-hour span, while the wider Chiba area logged 348mm over 12 hours up to 1:40 a.m. — the highest such total since national weather records began. In Chiba City's Chuo Ward, the 12-hour total had reached 367mm by 9:40 a.m., a record for that ward specifically.
How has the storm disrupted travel and power?
More than 20,000 households lost power as the storm moved through, and over 100,000 households were urged to evacuate on Thursday after the rain triggered landslides and additional outages. Several rail lines remained suspended into Friday morning and some major highways were closed. Around 1,800 people spent the night sheltering inside the Chiba Prefectural Government building, while passengers were also stranded at metro stations across the region.
Among the dead was a woman found inside a car that had become submerged on a flooded road, according to authorities. Two other people collapsed in the street and later died. Governor Kumagai said rescue teams would prioritise saving lives and continue search efforts.
Roughly 7,000 travellers were left stranded overnight at Narita Airport after the storm disrupted transport links to and from the facility.
An airport spokesperson said all flights were scheduled to resume normal operations on Friday. Flag carrier Japan Airlines said some flights could face delays but that it did not expect cancellations.
A resident of Ichikawa city in Chiba described the storm's sudden onset to NHK.
"[It] happened all of a sudden so it was a complete surprise," she said. "The power is out so I'm worried whether I can open my business in the next couple of days."
How does this compare with past flooding in the region?
According to the Japan Meteorological Agency, cited by Arab News Japan, this marked the first time the agency has ever issued its highest-level heavy-rain warning specifically for the Chiba region. Chiba has faced severe flooding before: a September 2023 event, detailed by Floodlist, saw Mobara City record 391.5mm of rain in 24 hours, breaking that city's previous record at the time. For context, Chiba City's average rainfall for the entire month of August is only about 115.7mm, according to figures referenced on Wikipedia, underlining just how extreme the latest totals were.
The rain arrived amid a wider run of storms across Japan and neighbouring countries this week, part of what forecasters had already flagged as an unusually active typhoon season. Earlier in the week, Japan, the Philippines and China were struck in quick succession by typhoons Dolphin, Chan-hom and Peilou. Dolphin brought heavy rain to Japan's Okinawa island, cutting power to tens of thousands of buildings, felling trees and grounding flights, before making landfall in eastern China over the weekend as the strongest typhoon to hit the country so far this year, prompting authorities there to evacuate more than a million people. In the Philippines, schools and government offices across much of the country's north were again closed this week because of ongoing flood risk.
What happens next?
The Japan Meteorological Agency has warned that unstable atmospheric conditions were likely to persist through early Saturday, 15 August, meaning additional heavy rain remained possible not only in Chiba but also across the wider Kanto region and in Nagano and Yamanashi prefectures, according to the Japan Times. The agency said it would continue monitoring lingering moisture from the weakened Typhoon No. 15 as the system dissipates, per Chosun Biz.
- Record hourly rainfall of over 100mm hit Chiba prefecture starting Thursday afternoon, 13 August 2026.
- Death toll reports vary: NHK, Kyodo and Asahi cited six dead and five injured, while later reporting put the figure at four dead, or five dead with one person missing.
- More than 20,000 households lost power and over 100,000 were urged to evacuate.
- About 7,000 travellers were stranded overnight at Narita Airport; flights were expected to resume normally on Friday.
- This was the first time Japan's Meteorological Agency issued its highest heavy-rain warning specifically for the Chiba region.
