PHILADELPHIA – The heat that blanketed much of the U.S. is expected to go from unbearable to merely very hot Sunday as temperatures from the Midwest to the East Coast drop from highs above 100 degrees down to the 90s.

Cooler air is sweeping 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 cities including 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.