The US military was set to join Japanese rescuers Sunday racing against the threat of more landslides to reach people still trapped by two big earthquakes, AFP reports.
At least 41 people are known to have died in the double disaster, with up to eight still missing - feared buried in shattered houses or under torrents of mud.
Rain hit the area around Kumamoto overnight, where officials have warned quake-loosened hillsides could be at risk of collapse as aftershocks continued to roil the ground.
The weather brought further misery to those who survived Thursday's initial quake and the bigger, more powerful tremor that hit early Saturday.