Mankato (KMKO)-The southern half of Minnesota is under a heat advisory issued by the National Weather Service, expected to remain in effect until Friday night.  The hot weather blanketed the southern part of the state yesterday, with Red Wing and Winona seeing high temps of 99 degrees.  Yesterday's high of 96 in Mankato set a record, beating the 87 degree reading in 2003.  Expect another record today, eclipsing the mark of 89 degrees set in 1999.