TOKYO (REUTERS) – Japan’s electricity grid creaked on Thursday (June 30) under the strain of Tokyo’s hottest June since records began, with the unexpected shutdown of a power plant raising fears that tens of millions of people could be deprived of power on another scorching day.

Temperatures of around 40 degrees Celsius were expected in some parts of greater Tokyo, home to 37 million people, on the sixth day of a heatwave that began after the earliest end to the capital’s rainy season in decades.

Maximum highs are not forecast to drop to 30 degrees Celsius before next Tuesday.

With power producers scrambling to bring nearly 50-year-old turbines out of mothballs, the closure of a 600-megawatt (MW) plant in northern Japan that sends supplies to Tokyo came with reserve power capacity hovering around 3 per cent – the level below which blackouts can occur.

Operator Joban Kyodo Thermal Power Company cited unexplained technical issues for the closure but said that parts of the plant had been restarted as of 1pm (noon Singapore time), media reports said.

It was expected to start generating power again in the evening.

A mid-morning estimate showed the reserve ratio of power generation capacity for the Tokyo area could fall as low as 3 per cent between 4.30pm and 5pm, according to national grid monitor OCCTO.

The industry ministry issued a power shortage warning for the fourth day in areas around Tokyo, urging households and businesses to save electricity, without stinting on air conditioning where it would endanger health, with heatstroke hospitalisations on the rise.

Temperatures this month have been the highest since record-keeping began in 1875.

The temperature in central Tokyo was 36.4 degrees Celsius at 1pm while the town of Hatoyama, north of the capital, sweltered at 39.7 degrees Celsius.

Turning off the lights

Some firms, like auto parts maker Yorozu Corp, are scaling back shifts to save power while others, like retailer Seven & i Holdings and tech giant Sony, have asked employees to save power by turning off lights and other devices.

Automaker Nissan Motor said it is operating generators at its Tochigi plant north of Tokyo from Wednesday through to Friday, while calling on offices and factories to save energy.

SoftBank Corp said it was easing up on the air-conditioning at its facilities to save power, letting the temperature rise to 26 degrees Celsius from 25 degrees Celsius.