* WHAT...For the Heat Advisory, heat index values up to 110. For the Extreme Heat Warning, dangerously hot conditions with heat index values of 110 or greater expected. * WHERE...Portions of southeast Arkansas, northeast Louisiana, and central, north central, northwest, southwest, and west central Mississippi. * WHEN...For the Heat Advisory, until 10 AM CDT this morning. For the Extreme Heat Warning, from 10 AM this morning to 9 PM CDT this evening. * IMPACTS...Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses. * ADDITIONAL DETAILS...The threat for dangerous heat continues through the end of this week. Additional heat advisories may be needed.