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A dog takes an early morning dip on the shore of Lake Michigan Wednesday, July 20, 2011 in Chicago, as Navy Pier is shown in the background. Much of the United States is trapped under a heat "dome" caused by a huge area of high pressure that's compressing hot, moist air beneath it, leading to miserable temperatures in the mid-90s to low 100s and heat-index levels well above 100 degrees. (AP Photo/Kiichiro Sato)

Nation wilts as heat wave spreads eastward

Americans withered under yet another day of searing sun Friday as a heat wave spread in earnest into the urban core of the Northeast, while warnings about excessive heat stretched from Kansas to Maine and the Carolinas. (AP)