Japan's Meteorological Agency is advising people in rain-hit areas of western Japan to take precaution for heatstroke.
Temperatures are forecast to rise above 30 degrees Celsius in many parts of the country on Thursday.
Weather officials say people taking shelter at evacuation centers and those involved in recovery work need to keep hydrated and take sufficient rest.
They warn that unstable atmospheric conditions caused by rising temperatures may bring thunderstorms to some areas.
The officials are also calling for caution against more landslides and flooding as the torrential rain has loosened the ground and mud and logs have blocked rivers.