Typhoon No. 24 collided with an autumn-rain front over southern Japan this week, producing rainfall totals on Yakushima Island that broke station records dating back decades and forced the Japan Meteorological Agency to invoke its most severe landslide alert. The Level 5 Landslide Disaster Special Warning, issued at 05:10 JST on September 5, told residents that unprecedented rainfall was occurring and that the probability of a landslide disaster having already occurred was extremely high. ## Records Shattered in a Single Night The numbers recorded on the island are extraordinary by any measure. Onoaida, one of the JMA's stations on Yakushima, measured 403 millimeters of rain in just 12 hours and 479.5 millimeters in 24 hours ending at 04:30 JST on September 5, according to the Japan Meteorological Agency. Both figures established new all-time records for the station. The total kept climbing. The 24-hour accumulation at Onoaida reached 490.5 millimeters by 05:30 JST, according to MBC South Japan Broadcasting, and rainfall since the beginning of the episode reached approximately 558 millimeters, nearly twice the station's normal rainfall for the entire month of September. The deluge was not limited to one station. JMA's other observation post on the island recorded 356 millimeters in 12 hours and 422 millimeters in 24 hours, setting September records, while all-time rainfall records also fell at Nakatane on neighboring Tanegashima. Radar analysis showed approximately 120 millimeters falling near Yakushima Town in the single hour ending at 19:30 JST on September 4, prompting JMA to issue its record short-duration heavy-rain information. ## Evacuations, Blackouts and a Port Filled With Driftwood The human impact mounted quickly as the ground saturated. Kagoshima Prefecture's situation report listed the evacuation order as covering 3,574 households and 6,228 people, issued at 20:19 JST on September 4, with eleven evacuation shelters operating in Yakushima Town. Infrastructure took direct hits. Heavy rain damaged part of the water-intake system serving the Nagamine district, cutting water service to as many as 289 households and forcing the town to open a distribution point at Nagamine Community Hall. Approximately 20 households remained without electricity as of 15:00 JST, according to the prefecture. Landslides were confirmed at several locations on the island, and swollen waterways carried large quantities of driftwood into Miyanoura Port, where debris accumulated around the harbor and its high-speed ferry terminal. ## A Warning System Working as Designed The alert sequence followed Japan's five-level warning framework precisely. JMA issued the Level 5 Landslide Disaster Special Warning at 05:10 JST on September 5, then replaced it with a Level 4 Landslide Disaster Danger Warning at 11:30 JST as the rain band moved east. Yakushima Town's evacuation action remained a separate Level 4 Evacuation Order. The distinction matters operationally. A Level 5 meteorological alert calls for immediate action to protect life but does not automatically trigger a municipal Level 5 Emergency Safety Measure, and Yakushima Town did not issue one. Kagoshima Prefecture moved on the administrative front as well. It established its Disaster Response Headquarters at 20:00 JST on September 4 as the episode intensified, and applied Japan's Disaster Relief Act to Yakushima Town effective September 4, citing circumstances in which numerous people had suffered or were at risk of harm to life or body. ## What Comes Next Although the Level 5 warning was no longer in effect, authorities continued urging residents to remain alert for landslides, flooding and further heavy rain because the ground remained saturated. Successive linear precipitation zones had developed over the Tanegashima-Yakushima area during the night, rapidly increasing the risk of flooding and landslides across the island chain. The episode demonstrates the function of Japan's layered warning architecture, in which meteorological alerts, municipal evacuation orders and prefectural disaster designations operate as separate but coordinated mechanisms. For the thousands of residents who spent the night in shelters, and for the hundreds still without running water, recovery begins only after the rivers recede and inspectors clear the slopes above their homes.