Weather officials are urging continued caution against heatstroke as temperatures are forecast to top 35 degrees Celsius in wide areas across Japan on Wednesday.
The Meteorological Agency says a high pressure system brought clear skies and raised temperatures mainly in eastern and northern Japan on Tuesday, while a tropical storm brought rain to parts of the country's west.
Daytime highs reached 38.4 degrees in Kumagaya City, Saitama Prefecture and Isesaki City, Gunma Prefecture, and 36.9 degrees in the cities of Fukushima and Osaka. The mercury hit 35 degrees in central Tokyo.
Weather officials are advising people to stay hydrated, avoid direct sunlight and use air conditioning.
The officials also say the rising temperatures and damp air have created unstable atmospheric conditions over wide areas, causing rain clouds to develop in some areas.
They are warning of sudden weather events, such as thunderstorms and gusty winds.