The sizzling temperatures in Japan last month saw a record number of people falling ill, according to the country's Fire and Disaster Management Agency.
Around 15,657 people were hospitalized due to heatstroke in June, the data showed.
The figure doubled from 2011 when 6,980 people reportedly fell ill due to rising temperatures, Tokyo-based Kyodo News reported on Wednesday.
The heatwave caused 17 deaths last month, surpassing 14 in 2011.
The historic temperatures recorded in Japan come amid an "unusual" early end to rainy season this year in the capital region, for the first time since 1951.
Tokyo last week recorded 147-year high temperatures for June.
Temperatures rose to 36.4 degrees Celsius (97.5 degrees Fahrenheit) in the last week of June.
