* WHAT...Peak heat index values up to 109. * WHERE...Portions of south central and southeast Texas. * WHEN...Until 7 PM CDT Tuesday. * IMPACTS...Hot temperatures and high humidity may cause heat illnesses. * ADDITIONAL DETAILS...Hotter conditions are expected on Wednesday with afternoon temperatures generally in the triple digits and peak heat indices in the 106 to 112 F range. This Heat Advisory will likely need to be extended through midweek.