An Excessive Heat Warning is still in effect., per the US National Weather Service Chicago Illinois. Oppressive heat and humidity is expected with peak heat indices, or 'feel like' temperatures, at or above 110 degrees. Limit time outside and take frequent breaks indoors or in the shade and hydrate. Check on relatives and neighbors. Children and pets should NEVER be left unattended in vehicles.
In addition, isolated strong to severe thunderstorm development is possible along a cold front late afternoon/early evening. Sharply falling temperatures are expected by the lake with cooler temperatures arriving overnight arewide.
Find out more about the warning signs and symptoms of heat related illnesses from the Center for Disease Control and Prevention.