* WHAT...Heat index values of 100 to 105 expected. This is the third day in a row with forecast or observed heat indices above 100 degrees.
* WHERE...Portions of northern and central Illinois near and south of I-80, as well as all of northwest Indiana.
* WHEN...Until 9 PM CDT /10 PM EDT/ this evening.
* IMPACTS...Hot temperatures and high humidity may cause heat illnesses especially after several days of dangerous heat.
* ADDITIONAL DETAILS...A cold front possibly accompanied by thunderstorms will move inland from Lake Michigan this evening leading to rapidly improving conditions.