Broiling temperatures in Japan saw the mercury hit a record 41 degrees Celsius yesterday, after at least nine people died from heatstroke at the weekend.
The nation's weather agency issued heat warnings for 38 of Japan's 47 prefectures, telling people to keep hydrated and use their air conditioners.
Sweltering temperatures contributed to the deaths of at least nine people from heatstroke on Saturday and Sunday, Japanese officials and media reports said.
Another heatwave last month claimed at least a dozen lives.
Japan's record temperature was registered at 1.42 pm in Shimanto, a Pacific coast city on the western island of Shikoku, the Japan Meteorological Agency said.
That broke the old high of 40.9 degrees in August 2007, registered in two central Japanese cities, the weather agency said.
Temperatures have soared above 40 degrees for the third straight day across parts of Japan as a Pacific high-pressure system covered most of the country.
The sweltering heat comes as Tokyo's energy costs have soared after Japan shut down its nuclear reactors in the wake of the Fukushima atomic crisis two years ago.
The move forced Tokyo to turn to pricey fossil-fuel alternatives to plug the gap.