Here’s why millions of Japanese are told to turn off lights but keep ACs on

Millions of Japanese were on Monday (June 27) urged to turn off lights at their homes and offices while “properly using air conditioning and hydrating during hot hours” as the country battles a heatwave.

According to local media reports, Japan’s central government on Sunday issued an “electricity supply shortage warning” for the first time ever under a new system, saying that the Tokyo area was expected to suffer a shortage Monday afternoon as temperatures in the Kanto region were likely to remain high.

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The government asked people to make efforts to save electricity, particularly between 3 pm and 6 pm Monday, including switching off unnecessary lights while also taking measures to prevent heatstroke, Japan Times reported.

According to Scott Duncan, a meteorologist from Scotland, “historic and dangerous heatwave” is gripping Northeast Asia, and has broken the national June record in Japan. He said that Japan recorded its first 40° Celsius ever in the month of June.

Historic and dangerous heatwave gripping Northeast Asia breaks national June record in Japan 🇯🇵

The first 40°C ever to be recorded in the country in the month of June. pic.twitter.com/E4KnKkSLYj

— Scott Duncan (@ScottDuncanWX) June 25, 2022

The Ministry of Economy, Trade and Industry expects demand for power to be “severe” on Monday afternoon local time. It said people should switch off unnecessary lights but still use air conditioning to avoid heatstroke, according to a BBC report.

June marks the start of summer in Japan, with temperatures typically staying below 30° C during the month, the report added.

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In a statement on Sunday, the ministry said that excess generating capacity for electricity was expected to drop to 3.7% on Monday afternoon in Tokyo and eight surrounding prefectures. It views a buffer of 3% as necessary for a stable power supply.

More than 250 people were taken to hospitals in Tokyo over the weekend for treatment of heat stroke, according to a report in Mainichi newspaper.

Japan’s weather officials warned that a record-level heatwave is forecast for the next two weeks after the rainy season apparently ended unusually early in some regions. The Japan Meteorological Agency issued the warning after announcing on Monday that it believes the season has ended in the Kanto-Koshin region, which includes Tokyo, as well as in Tokai and southern Kyushu, report Japanese public broadcaster NHK.

On Sunday, the mercury rose above 36 degrees Celsius in parts of Tokyo, Saitama, Tochigi and Ibaraki prefectures, just a day after Japan saw its highest-ever temperature in June, according to Japan Times.

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Temperatures rose above the country’s “extreme heat” threshold of 35° C in a number of areas on Sunday, hitting 36.8° C in both Sano, Tochigi Prefecture, and Isesaki, Gunma Prefecture, and 36.4° C in Koshigaya and Kumagaya in Saitama Prefecture. Tokyo’s Nerima Ward also posted a 36.4° C high. The mercury also rose to 36.3° C in the town of Daigo, Ibaraki Prefecture, and 36.2° C in Tokyo’s Chiyoda Ward, the report added.

In July 2018, at least 65 deaths were recorded due to the heatwave in Japan. More than 22,000 people were taken to hospital with heat stroke, nearly half of them elderly, officials said, according to a BBC report.