* WHAT...For the Heat Advisory, heat index values of 100 to 106. For the Extreme Heat Warning, dangerously hot conditions with heat index values of 110 to 116. * WHERE...Portions of southern Illinois, western Kentucky, and southeast Missouri. * WHEN...For the Heat Advisory, until 11 AM CDT Tuesday. For the Extreme Heat Warning, from 11 AM to 7 PM CDT Tuesday. * IMPACTS...Heat related illnesses increase significantly during extreme heat and high humidity events. Hot temperatures and high humidity may cause heat illnesses.