The mercury shot up to 35 degrees in two municipalities in eastern Japan on Saturday, while many other parts of the nation also experienced summer temperatures due to a high pressure system that brought clear skies.
The temperature topped 30 degrees at more than 250 observation points across the country, hitting 35.2 degrees in Hatoyama, Saitama Prefecture, and 35.1 degrees in Tatebayashi, Gunma Prefecture, the Meteorological Agency said.
The temperatures at the two locations marked the first this year of what the agency calls a day of "extreme heat" — defined as a day that reaches 35 degrees or higher.
Tokyo recorded 33 degrees, the hottest so far this year, while Tajimi, Gifu Prefecture, registered 34.2 degrees.
The agency is calling on people to remain hydrated to counter heat stroke or heat exhaustion.
Cloudy skies are forecast to prevail particularly in western Japan on Sunday because of the approaching seasonal rain front in the Pacific, according to the agency.