Japan's government has urged people in Tokyo to turn off unused lights and conserve energy while the country endures unseasonably hot temperatures.
In Isezaki, north of Tokyo, the temperature rose to 40.2°C on Saturday, the highest ever for June. Temperature in downtown Tokyo rose to nearly 35°C on Monday, higher than the forecast Sunday of 34°C.
The sultry temperatures would be considered mild compared to some south and southeast Asian countries, but they are adding to worries over power shortages over the summer.
Tokyo's local government urged people living in the region to "turn off unused lights while using air conditioners" between the peak hours of 3pm to 6pm.
Kaname Ogawa, director of electricity supply policy at Japan's economy and industry ministry, said demand on Monday was bigger than expected because the temperature exceeded Sunday’s forecast. A similar warning was issued for Tuesday.
“We are struck by unusual heat for the season,” Mr Ogawa said. “Please cooperate and save as much power as possible.”
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Mr Ogawa, however, said people should use air conditioning appropriately and take precautions against heat stroke.
More than 250 people were taken to hospitals in Tokyo over the weekend for treatment of heat stroke, according to The Mainichi, a local newspaper.
Heat stroke is a big concern since many older Japanese tend to avoid using air conditioning, partly out of habit and partly to avoid running up big electricity bills. Older Japanese homes also tend to lack insulation and are stiflingly hot in the summer and very cold in the winter.
Weather officials announced the earliest end to the annual summer rainy season since the Japan Meteorological Agency began keeping records in 1951. The rains usually temper the summer heat, often well into July. With hot air coming from a powerful high atmospheric pressure system stalled over the Pacific Ocean, high temperatures were expected through early July, the meteorological agency added.
The power supply is relatively tight after Japan idled most of its nuclear reactors after 2011 meltdowns in Fukushima, Japan.
Prime minister Fumio Kishida’s government has been pushing to restart more nuclear reactors that have passed upgraded safety standards.
Japan also faces a potential shortage of fossil fuel imports amid sanctions against Russia over its invasion of Ukraine.
Tokyo has also been closing down old coal plants to meet promises for reducing carbon emissions.
Some coal-fired plants serving the Tokyo were taken offline for repairs after a strong earthquake in mid-March. The government warned of potential problems in late March, though no actual outages occurred.