Residents from Iowa to New Jersey spent the day trying to stay cool. They dipped into the water, went to the movies, and rode the subway just to be in air conditioning.
If people ventured outside to do anything, they did it early. But even then, the heat was stifling.
"It was baking on the 18th green," said golfer Zeb Rogerson, who teed off at 6 a.m. at an Alexandria, Va., golf course but was sweltering by the end of his round.
Officials said the heat caused highways to buckle in Illinois and Wisconsin. In Maryland, investigators said heat likely caused rails to kink and led a Metro train to partially derail in Prince George's County on Friday afternoon. No one was injured, and 55 passengers were safely evacuated.
Micah Straight, 36, brought his three daughters to dance in jets of water spurting from a "sprayground" near Philadelphia's Logan Square fountain to cool off.
"We got here early, because I don't think we'll be out this afternoon – we'll be in the air conditioning," he said. "So I wanted to get them out, get some sunshine, get tired."