* WHAT...Dangerously hot conditions with heat index values 105 to 110. * WHERE...All of southern Illinois, southwest Indiana, western Kentucky, and southeast Missouri. * WHEN...Until 8 PM CDT /9 PM EDT/ Saturday. * IMPACTS...Heat related illnesses increase significantly during extreme heat and high humidity events. * ADDITIONAL DETAILS...Overnight low temperatures in the mid 70s will provide little relief from the heat.