The evacuation order came as torrential rain continues to pummel southwest Japan, with Kyushu Island, which comprises Kagoshima City, the capital of Kagoshima Prefecture, one of the hardest-hit regions.
Japan's Meteorological Agency (JMA) had previously warned of torrential rain continuing to inundate the Kyushu region, with people in the area already on alert for possible natural disasters triggered by the extremely heavy rainfall.
Prior to Wednesday's evacuation order being issued, people in affected areas were being asked to pay attention to the latest weather warnings and to advice from local officials and to take preemptive measures to ensure their safety where necessary.
The weather agency has said that a seasonal front has been lingering over the region in the southwest of the country, with storm clouds developing owing to warm and humid air flows.
Kagoshima City, where the evacuation order was issued, had logged more than 40 millimeters of rain between 7:00 a.m. and 8:00 a.m. local time on Wednesday morning, with officials warning of possible mudslides in the wider prefecture.
The extreme downpours will become more active until Thursday, the JMA said, with as much as 80 millimeters per hour expected for some areas in Kyushu, which is as much as the average amount of rainfall for the region for the entire month of July.
Ryuta Kurora, a senior Japan Meteorological Agency (JMA) forecaster, told a hastily convened press conference a day earlier that torrential rain is expected through Thursday, with the southwestern main island of Kyushu likely to be the hardest hit.
Kurora said that residents in the affected areas should be aware that the situation could be life threatening and evacuations by residents should be swift in light of possible mudslides, flooding, lightening and tornadoes.
The JMA has also warned of possible "deep-seated" mudslides in areas that become inundated, which refers to the entire shift of the bedrock of mountains and slopes, leading to potentially devastating landslides.
Residents in areas that have and will be pummeled by rain over the next few days should identify where their nearest evacuations center are, Kurora said, adding that once an emergency evacuation order is issued, it will probably be too late.
"We want people to understand that a situation in which they have to protect their own lives is imminent," Kurora said underscoring the need for local residents to take preemptive measures if necessary.
Around 850,000 people were previously urged to evacuate from nearly 400,000 homes in the hardest-hit regions across Kagoshima, Kumamoto and Ehime prefectures, local media reported Tuesday.
The evacuation advisory issued Wednesday was level four, the second-highest on the weather agency's scale which peaks at five, which calls on all people to evacuate immediately.
Based on this, local officials said those under advisement should swiftly move to emergency shelters for safety.
Advisories have been given for people in inundated areas to remain vigilant for potential for heavy flooding, especially in low-lying areas and near rivers that might burst their banks. People have also been put on high alert for mudslides.
