Record-breaking heat grips much of eastern US (AP)

U.S. Customs and Border Patrol agent Sanchez drinks water from a gallon jug as he patrols along the Rio Grande in Penitas, Texas  Wednesday, June 8, 2011.   (AP Photo/Eric Gay)AP - The mercury climbed into the 90s across half the country Wednesday in a record-breaking blast of August-like heat, forcing schools with no air conditioning to let kids go home early and cities to open cooling centers. And scientists say we had better get used to it.