PHILADELPHIA — The heat that blanketed much of the U.S. began to ease up from unbearable to merely hot Sunday as temperatures from the Midwest to the East Coast dropped from highs above 100 degrees down to the 90s.

Cooler air swept southward in the eastern half of the country, bringing down some temperatures by 15 or more degrees from Saturday’s highs, which topped 100 in Philadelphia, Washington, St. Louis, Indianapolis and Louisville, Ky.

For many areas, the cooler temperatures were ushered in by thunderstorms that knocked out power to thousands. In New Jersey, a line of strong, fast-moving storms knocked out power to nearly 70,000 on Saturday night.

The heat of the past several days has been blamed for at least 35 deaths across the country. A 4-month-old girl died and a 16-month-old girl was hospitalized in suburban Indianapolis after both were found trapped in cars in 105-degree heat Saturday.

If Americans 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.