Japan struggles to deliver flood relief

Rescuers are still searching for over 80 people who are missing after heavy rainfalls in Japan

Japan is struggling to restore utilities and bring relief to the victims of its worst floods in 36 years, facing health risks from hot temperatures and a lack of water.

Torrential rains unleashed floods and landslides in western Japan last week, killing 127 and forcing several million from their homes.

Power supply has resumed to all but 3,500 customers, but more than 200,000 remain without water under scorching sun, with temperatures set to hit 33 degrees Celsuis in some of the hardest-hit areas.

"There have been requests for setting up air conditioners due to rising temperatures above 30 degrees today, and at the same time we need to restore lifelines," Finance Minister Taro Aso said.

As rescuers carry on the grim search for victims, survivors recounted narrow escape stories.

"It was close. If we had been five minutes later, we would not have made it," said Yusuke Suwa, who fled by car with his wife early on Saturday.

The death toll is rising and 63 people are still missing, public broadcaster NHK said.

The government has set aside 70 billion yen $A846 million) in infrastructure funds to respond to the disaster, with more in reserve.

A new evacuation order went out on Tuesday in a part of Hiroshima prefecture, after a river blocked by debris overflowed its banks, affecting 23,000 people.