All across the region, people tried to cope. The men’s shelter in northeast Washington where William Burrell was staying lost power and hadn’t regained it by Saturday morning. “The fans, the air-conditioning, all of it. It was burning up,” he said. “So they opened the doors to try to get some air to circulate through, but by that time the thunderstorm had stopped, and there was the littlest, light breeze, but it wasn’t enough to cool everybody off that was in there.”

Julie B. Rubenstein, a lawyer who lives in Northern Virginia, said that after suffering through the night with no power and no air-conditioning, she retreated to her office. She described how friends who rushed to grocery stores to get bags of ice found only long lines and limited supplies. At one point, she said, a “near-fight” broke out over a bag of ice.

“It is great that I had an office I could go to,” she said, “but so many people don’t.”

In Virginia, authorities opened 90 air-conditioned shelters where residents could go to escape the heat.

There were reports of deaths from the storm and heat in New York, New Jersey, Maryland, Tennessee, Ohio and Kentucky. In Clark County, Ky., a man was killed when a tree fell on him, officials said.

In Chandlersville, Ohio, a woman died when her barn collapsed on her as she went to check on her animals.

In southern New Jersey, two young cousins were killed when a tree fell on the tent they were camping in, according to The Associated Press.