A man stands in a fountain in Washington Square Park on July 18, in New York City. Temperatures were expected in the upper 90's during another heat wave in the city. Mario Tama/Getty Images hide caption

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John Rohlfing, 38, takes a drink as he works on the construction of his new home Thursday in North Aurora, Ill. He started at 6:00 a.m. and quit at 11:00 a.m. because of triple-digit temperatures. Robert Ray/AP hide caption

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In Silver Spring, Md., on Monday, Matt MacCartney was one of many workers dismantling fallen trees that took down power lines. Chip Somodevilla/Getty Images hide caption

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Volunteer John Kelley (left) leads an exercise class at a senior center in Oklahoma on Monday. Centers such as these offer seniors a cool place to go during heat waves. Sue Ogrocki/AP hide caption

itoggle caption Sue Ogrocki/AP