Less than a month after flooding killed more than 200 people in western Japan, a heat wave has now brought unprecedented scorching temperatures, killing at least 30 people and sending thousands nationwide to hospitals.

Some areas of the country reached as high as 40.7 degrees Celsius, while in the ancient capital of Kyoto it peaked at 39.8 Celsius after days of temperatures at 38 degrees or more, a level unseen since record-keeping began.

The Japan Times reported at least 10,000 people had been taken to hospital with heat stroke and related symptoms since the temperatures began to soar.

The Education Ministry warned schools to take precautions against heat stroke following the death of a six-year-old boy after attending a class last week.

Thousands still homeless from floods

It's the second deadly weather event this month in Japan.

At least 218 are dead and 12 still missing after flooding on the west coach of Japan.

There are still about 4,500 people living in emergency shelters in the wake of the flooding and Japanese authorities were considering housing the displaced people on a cruise ship, according to the Japan Times.

Millions were forced to evacuate due to floods and landslides, with most of the 200 people who have died coming from the Hiroshima and Okayama prefectures.

A resident is rescued from a submerged house in Kurashiki.

The Japan Meteorological Agency said as much as 10 centimetres of rain per hour fell on large parts of south-western Japan.

After the flooding subsided and the clean-up began, authorities were desperate to restore utilities in the face of temperatures starting to rise above 30 degrees.

Women use a parasol at a shopping district in Tokyo.