* WHAT...Peak Heat Index values up to around 100 degrees this weekend. * WHERE...All of southern Illinois, southwest Indiana, western Kentucky, and southeast Missouri. * WHEN...Until 7 PM CDT /8 PM EDT/ Sunday. * IMPACTS...Hot temperatures and high humidity may cause heat illnesses. * ADDITIONAL DETAILS...The Heat Advisory was extended thru the weekend due to the prolonged high heat conditions that have basically been ongoing for the entirety of the past week; this continues to heighten the risk of heat-related health impacts.