Three hundred million people were left sweltering without electricity after northern India’s power grid went out Monday. Hundreds of trains, including New Delhi’s Metro system, went down when the grid collapsed under the pressure of a hot summer, and highways saw miles of bumper-to-bumper traffic without power for traffic lights. India’s power minister, Sushil Kumar Shinde, said late Monday morning that the eight northern states affected by the outage had at least 60 percent of their power back and that the rest should be restored by late afternoon. The outage—one of the worst blackouts in a decade—marked the first time the country’s northern grid had gone down since 2001. Low rainfall has contributed to higher temperatures recently, increasing the amount of energy used for fans and air conditioning.