Japan’s stifling temperature caused the most number of heatstroke cases the country has ever seen amid electricity-saving measures due to power shortages, the Wall Street Journal reports.

Temperatures in large parts of the country hit Japan’s Meteorological Agency’s warning level of over 35 degrees Celsius (95 degrees Farenheit). According to the Fire and Disaster Management Agency, July saw the highest ever number of people hospitalized for heatstroke, with figures reaching over 21,000, up from 18,000 of the same period last year. The FDMA reported 39 deaths from heatstroke-related illnesses and 439 severe cases in the period from May 28 to August 5. About 43% of the patients were elderly.

The Japanese government urged citizens to conserve energy as it faces power shortages after a nuclear shut down in the country. The Journal reported that many people who were hospitalized due to heatstroke did not own or use air conditioning.