An Excessive Heat Watch issued for the entire Chicago area this week has been upgraded to an Excessive Heat Warning.
The warning remains in effect through 7 p.m. Friday.
The heat wave expected to stretch across many cities in the central U.S. in the coming days will bring the hottest weather of the year so far with extreme triple-digit heat.
Thursday temperatures are forecast to soar into the mid 90s, but with high humidity, things will feel even hotter.
The National Weather Service warned that maximum heat values could reach between 105 and 115 degrees. The heat index is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature.
In northwest Indiana, a Heat Advisory was also issued. The advisory, which remains in effect from noon Thursday to 7 p.m. Friday, warns of heat index values between 103 and 108 degrees.
For Ogle, Lee, LaSalle, Grundy, Kankakee, Livingston, Iroquois and Ford counties, an Excessive Heat Watch will also continue until Saturday afternoon.
Sweltering conditions remain through Friday, for another windy, brutally hot and extra humid day. Temperatures hover in the mid 90s with heat index values in the dangerous category once again, between 105 to 115 degrees.
The National Weather Service warns heat-related illnesses such as heat strokes, heat cramps and heat exhaustion are possible in the extremely hot and humid weather.
More people die each year from heat than lightning, tornadoes, hurricanes and floods, according to weather officials.
Residents are urged to reduce strenuous activity, drink plenty of water and other non-alcohol fluids and avoid getting to much sun.
The temperatures fall for the weekend, but only slightly. Saturday will be hazy, hot and humid with the chance of thunderstorms developing late in the day. Highs could reach into the mid-90s.
On Sunday the Chicago area will see a small relief from the heat. A partly sunny and less humid day is in store with highs in the mid 80s, and cooler along the lakefront.