<p>Japan braced on Wednesday for its hottest day yet of a record-breaking heatwave, as Prime Minister Fumio Kishida called for a ramp-up of nuclear power use amid fears of a shortage of electricity to keep air conditioners whirring.</p>.<p>As some manufacturers announced plans to scale back production to save power, temperatures of around 40 C were predicted in areas surrounding Tokyo on the fifth day of the capital's worst June heatwave since records began in 1875.</p>.<p>The Japan Meteorological Agency forecast that temperatures there won't drop back to 30 C until July 5.</p>.<p>"The electricity demand and supply situation is expected to be the toughest in the last three days (of this week)," an industry ministry official told reporters.</p>.<p>All additional measures to boost supply had been incorporated, according to national grid monitor OCCTO, whose mid-morning estimate showed the reserve ratio of power generation capacity for the Tokyo area likely to fall as low as 2.6% between 4.30 pm and 5 pm on Wednesday - under the minimum 3% threshold deemed necessary to ensure stable supply.</p>.<p>The government signalled a power shortage warning for the fourth consecutive day on Thursday for Tokyo and surrounding areas although the supply-demand balance would likely be less tight with additional capacity coming on stream.</p>.<p>Prime Minister Kishida said he would do his utmost to secure enough supply, telling a news conference he would make the greatest possible use of nuclear power as long as safety was assured.</p>.<p>Most of Japan's nuclear plants have been halted since the March 2011 tsunami that set off the Fukushima nuclear accident.</p>.<p>Meanwhile, power companies are rushing to restart thermal power plants that have been shut down and calls are rising for additional use of alternate energy sources, including restarting reactors.</p>.<p>As officials again called on households to save electricity where possible - without stinting on air conditioning where it would endanger the health of the vulnerable - auto parts maker Yorozu Corp said it would close its manufacturing plants for at least two days a month from July through September.</p>.<p>Seven & i Holdings said it was asking 7-Eleven stores in and around Tokyo to take further power-saving measures such as dimming signboards and turning off ventilation fans when deep-frying equipment was not in use during the 3-8 pm crunch time.</p>
<p>Japan braced on Wednesday for its hottest day yet of a record-breaking heatwave, as Prime Minister Fumio Kishida called for a ramp-up of nuclear power use amid fears of a shortage of electricity to keep air conditioners whirring.</p>.<p>As some manufacturers announced plans to scale back production to save power, temperatures of around 40 C were predicted in areas surrounding Tokyo on the fifth day of the capital's worst June heatwave since records began in 1875.</p>.<p>The Japan Meteorological Agency forecast that temperatures there won't drop back to 30 C until July 5.</p>.<p>"The electricity demand and supply situation is expected to be the toughest in the last three days (of this week)," an industry ministry official told reporters.</p>.<p>All additional measures to boost supply had been incorporated, according to national grid monitor OCCTO, whose mid-morning estimate showed the reserve ratio of power generation capacity for the Tokyo area likely to fall as low as 2.6% between 4.30 pm and 5 pm on Wednesday - under the minimum 3% threshold deemed necessary to ensure stable supply.</p>.<p>The government signalled a power shortage warning for the fourth consecutive day on Thursday for Tokyo and surrounding areas although the supply-demand balance would likely be less tight with additional capacity coming on stream.</p>.<p>Prime Minister Kishida said he would do his utmost to secure enough supply, telling a news conference he would make the greatest possible use of nuclear power as long as safety was assured.</p>.<p>Most of Japan's nuclear plants have been halted since the March 2011 tsunami that set off the Fukushima nuclear accident.</p>.<p>Meanwhile, power companies are rushing to restart thermal power plants that have been shut down and calls are rising for additional use of alternate energy sources, including restarting reactors.</p>.<p>As officials again called on households to save electricity where possible - without stinting on air conditioning where it would endanger the health of the vulnerable - auto parts maker Yorozu Corp said it would close its manufacturing plants for at least two days a month from July through September.</p>.<p>Seven & i Holdings said it was asking 7-Eleven stores in and around Tokyo to take further power-saving measures such as dimming signboards and turning off ventilation fans when deep-frying equipment was not in use during the 3-8 pm crunch time.</p>