* WHAT...For the first Heat Advisory, heat index values up to 109 expected. For the second Heat Advisory, heat index values up to 109 expected. * WHERE...Portions of central, east central, northwest, southeast, southern, southwest, and western Oklahoma and northern Texas. * WHEN...For the first Heat Advisory, until 9 PM CDT this evening. For the second Heat Advisory, from 11 AM to 9 PM CDT Tuesday. * IMPACTS...Hot temperatures and high humidity may cause heat illnesses.