More than 1 million homes and businesses in a swath from Indiana to Virginia remained without power early on Wednesday, five days after deadly storms tore through the region.
The outage meant no July 4 holiday for thousands of utility workers who scrambled to restore power across the region.
Much of the afflicted areas faced yet another day of scorching heat, with the National Weather Service forecasting temperatures from 90 Fahrenheit (32 Celsius) to more than 100 F (37.7 C) from the Midwest to the Atlantic Coast.
Violent weekend storms and days of record heat have killed at least 23 people in the United States since Friday. Some died when trees fell on their homes and cars, and heat stroke killed others.
Utilities warned that some people could be without power - and unable to run their air conditioners - for the rest of the week.
In the District of Columbia, about 5,000 customers of local power company Pepco were still without power on Wednesday morning, and the city was distributing food to people who were unable to cook at home. Closer to 50,000 Pepco customers in suburban Maryland were still in the dark.
But the region still most affected, however, was West Virginia and the neighboring Blue Ridge Mountain section of Virginia, accounting for close to half of the lingering outage.
More than 315,000 customers of Appalachian Power and MonPower in West Virginia - roughly a third of the homes and businesses served by the two utilities in the state - remained in the dark overnight Tuesday. Just over the state line in the mountains of western Virginia, more than 135,000 Appalachian and Dominion Virginia Power customers had no power early Wednesday.
Appalachian said in a statement late Tuesday that 2,900 employees were scrambling to restore power in its area and would work through the Independence Day holiday. The other utilities also pledged to keep crews working - some in 16-hour shifts - until the electricity was restored.
Much of the damage to the power grid was blamed on last weekend's rare "derecho," a big, powerful and long-lasting wind storm that blew from the Midwest to the Atlantic Ocean.
The death toll from the storms and high temperatures climbed to at least 23 with five more heat-related deaths reported in Nashville, Tennessee; Kansas City, Missouri; Philadelphia; and Virginia.
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