The most expansive U.S. heat wave of the season will peak over the next few days before retreating into the South.  On July 27-28, temperatures could peak near 105°F as far north as the middle Mississippi Valley.  Farther east, late-week temperatures could reach 100°F as far north as the mid-Atlantic.  Starting on Friday, relief from the heat will reach the northern Corn Belt, with cool air making additional progress into the Midwest and Northeast during the weekend. 

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