Temperatures are expected to top out at 100 to 105 degrees Thursday and Friday, but the heat index could top out at 108 to 118 degrees, according to the National Weather Service. 

An excessive heat warning is in effect for Darien until 10 p.m. Friday. 

An air quality alert has also been declared for Thursday and Friday. Elevated ozone levels and poor air quality will increase the stresses on the body from the heat. This is true especially for children, the elderly and those with pulmonary or respiratory conditions. These groups should limit their exposure to outdoor air until Saturday. 

Prolonged exposure to the heat will be dangerous, according to the NWS, and can cause sunstroke, heat cramps or heat exhaustion.

If you need to work outside, reschedule activities for early morning or evening. Wear light-weight and loose-fitting clothing and drink plenty of water. 

Take frequent breaks in shade or in an air-conditioned space. 

Stay out of the sun and check on relatives and neighbors. Pets and children should not be left unattended in cars as the interior can reach lethal temperatures in a matter of minutes. 

Cooling centers 

In Darien, residents can seek shelter from the heat at the Darien Police Department or Indian Prairie Public Library. For more information, call the police department at 630-971-3999 or the library at 630-887-8760.

For a complete list of DuPage County cooling centers, click on the PDF at the top of this story.