Last week, the temperature near Tokyo went over 40ºC for the first time in June. It was a record 40.2ºC in a city north of Tokyo. People are using air conditioners more. This is making it difficult for power companies to produce electricity. Japan's government has asked people to use less electricity. It said: "We ask the public to reduce energy consumption during the early evening hours." It wants people to turn off lights from 3 pm to 6 pm.

Japan's heat wave will continue. The rainy season just finished. It's the earliest since records began in 1851. This means there'll be a long, hot summer. The government said: "Please cooperate and save as much power as possible." A power company warned there could be power shortages. There is also a risk of people getting heatstroke. More than 250 people were taken to hospital in Tokyo over the weekend with heatstroke.