...A Heat Advisory remains in effect for the entire Four State Region through 7 PM CDT Sunday... ...HEAT ADVISORY REMAINS IN EFFECT UNTIL 7 PM CDT SUNDAY... * EVENT...An upper level heat ridge will begin building east into the region Sunday, resulting in afternoon temperatures again climbing into the mid 90s to near 100 degrees. Southerly winds will maintain the high humidity values this afternoon and again Sunday, with resultant heat indices ranging from 105 to 110 degrees. Limited relief from the heat is expected tonight, with low temperatures only falling briefly into the mid and upper 70s. * TIMING...Through 7 pm CDT Sunday. * IMPACT...High heat index readings will increase the risk of heat-related illnesses.