TOKYO - Three cities in central Japan on Tuesday reached 40 C, officially marking the country's first "kokushobi," or "cruelly hot day," since the weather agency introduced the term earlier this year to warn the public of extreme heat.

As a high-pressure system covered much of the Japanese archipelago, Tajimi and Gujo in Gifu Prefecture recorded temperatures of 40.3 C and 40.0 C, respectively, while the mercury in Toyoda in Aichi Prefecture climbed to 40.1 C, according to the Japan Meteorological Agency.

Coined in April, the term "kokushobi" refers to days when temperatures reach 40 C and is intended to more effectively alert the public to dangerous heat.

The agency said it expects temperatures to remain high in many parts of the country from Wednesday onward and urged the public to take precautions against heat-related illness.

The persistent heat has apparently already claimed lives, with two men -- one in his 70s in Odawara, Kanagawa Prefecture, and another in his 40s in Sanjo, Niigata Prefecture -- found collapsed on the street Monday and later confirmed dead at hospital.

On Tuesday, a woman in her 80s died from heatstroke in Mitsuke, Niigata Prefecture, according to local officials. The woman was found collapsed in her home when a staff member from a regional elder care center visited her.

Of the country's 914 observation points, 731 had recorded maximum temperatures of 30 C or higher as of 3 p.m., with 272 qualifying as "moshobi," which literally translates as "extremely hot day," excluding those separately classified as "kokushobi."

According to the agency, the high-pressure system began covering much of the country around Sunday, warming the air at both the surface and in the upper atmosphere and causing temperatures to rise.

Other areas that recorded temperatures close to 40 C included Nagoya, which reached 39.7 C, and Kumagaya in Saitama Prefecture, which recorded 38.6 C, it said.

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