* WHAT...For the Extreme Heat Warning, dangerously hot conditions with heat index values up to 114 expected. For the Heat Advisory, heat index values up to 108 expected. * WHERE...Portions of south central and southeast Texas. * WHEN...For the Extreme Heat Warning, until 8 PM CDT this evening. For the Heat Advisory, from 8 PM this evening to 10 PM CDT Saturday. * IMPACTS...Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.