The Japanese government warned on Sunday that electric power supplies would be strained in the Tokyo area on Monday, calling on people to save energy as scorching summer heat batters the capital.
In Tokyo and eight nearby prefectures in eastern Japan, excess generating capacity will drop as low as 3.7% for half an hour on Monday afternoon until 5 p.m. (0800 GMT), according to estimates released by the Ministry of Economy, Trade and Industry (METI). A buffer of 3% is considered the minimum required for a stable power supply.
The ministry urged users to curb power consumption between 3 p.m. and 6 p.m. to avert a possible power crunch.
"Please save as much power as possible, such as by turning off lights that are not in use," it said in a statement.
The ministry also urged care to avoid heat stroke with appropriate use of air conditioning.
As of mid-afternoon on Sunday, 46 people in Tokyo had been taken to hospital with suspected heat stroke, public broadcaster NHK said.
Separately, a 94-year-old man in Kawagoe city, 20 kilometers (12 miles) northwest of Tokyo, died of suspected heat stroke after he was discovered unconscious in his non-air-conditioned room on Saturday, NHK said.
Isezaki city, 85 kilometers (53 miles) northwest of Tokyo, logged Japan's highest temperature ever for June on Saturday, breaking above 40 degrees Celsius (104 degrees Farenheit), according to the Japan Meteorological Agency.
Japan's power supply has been tight with many of its nuclear power plants still shut after the tsunami and Fukushima nuclear disaster of 2011, while aging thermal power plants are being closed in part to reach its goal to cut carbon dioxide emissions. Read full story
The country also faces a potential shortage of fossil fuels, including liquefied natural gas, due to the conflict in Ukraine and sanctions against Russia.
