Japan and South Korea were struck by a series of extreme rainfall events last week, shattering long-standing records and triggering emergency evacuations across both countries. On 13 August, the city of Chiba, located near Tokyo, recorded 115mm of rainfall within a single hour — a new record for the area — while the nearby city of Sakura also broke its own one-hour record with 97mm. Authorities responded by issuing a level 5 emergency warning for heavy rain, the highest alert level available and the first time such a warning has been issued since the system was introduced in May.
The consequences were severe across the greater Tokyo region. More than 100,000 households were ordered to evacuate, and over 20,000 homes in Chiba prefecture lost power. Thousands of travellers were stranded at Narita airport, one of Japan's main international gateways. Thirteen people have been confirmed dead — at least three of whom were found trapped inside their vehicles — and one person remains missing. The Japan Meteorological Agency described the event as an "unprecedented level" of heavy rain, a notable designation for a country already accustomed to intense summer downpours caused by warm, moisture-laden air from the north Pacific colliding with cooler air masses.
South Korea was similarly affected. In the city of Geoje, a port city on the country's southeastern coast, 124.5mm of rain fell within a single hour in the early hours of 17 August. Total rainfall through the night exceeded 400mm — a figure that would be extraordinary by almost any standard. Emergency services were deployed as floodwaters inundated roads and communities across the region.
The extreme weather is not yet over for the region. Tropical storm Saudel, which developed near Micronesia and has since been strengthening, is forecast to intensify into a powerful or potentially violent typhoon over the coming days. Travelling on a north-westerly track, it is expected to pass close to or make landfall on the Northern Mariana Islands, a chain of islands in the western Pacific, before turning towards Okinawa prefecture — the group of islands forming Japan's southernmost territory — early next week. Authorities in affected areas have already been placed on alert.
The scale and frequency of these events underscores a broader pattern of intensifying extreme weather across East Asia during the summer monsoon season. With climate conditions continuing to amplify the energy available to storm systems, meteorologists warn that events once considered unprecedented may become increasingly common benchmarks rather than true outliers.