Excessive heat warnings will continue for much of the Desert Southwest through Monday. Here, Maria Wieser of Italy drinks water while sightseeing in Death Valley National Park on Friday. Chris Carlson/AP hide caption

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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