According to initial official data, a historical heat wave in June resulted in more than 15,000 individuals being sent to hospitals in ambulances throughout Japan with heatstroke or heat dehydration, a record high for the month.

A record-high June temperature was measured at 338 of the Japan Meteorological Agency’s 914 monitoring stations throughout the month. Around 70% of instances were recorded between June 24 and June 30, when the public was sweating in a heat wave.

The Fire and Disaster Management Agency said that on Tuesday that the total number of people hospitalized in June was 15,657, which is a significant increase from the previous high of 6,980 in 2011 and the greatest figure since comparable statistics began being available in 2010.

Of the total, more than 50% were 65 years of age or older, and 40% had signs at home.

After already being taken to hospitals, a record 17 individuals passed away, exceeding the 14 deaths in 2011.

“On top of the unusual heat wave, some people may have had difficulty adjusting to the sharp rise in temperature,” an agency official said, keeping hydrated and taking regular rest are advised in order to prevent heatstroke.

The data showed that although 5,261 persons experienced mild symptoms and were hospitalized for a shorter amount of time, 439 people needed a stay of much more than three weeks.

According to the data, there were 24,495 patients transferred to hospitals total from May 1 to July 3, an increase of 3.4 times over a year previously.