The National Weather Service issued an Excessive Heat Warning for all of northern Illinois in effect from noon Thursday to 7 p.m. Friday. A Heat Advisory has also been issued for northwest Indiana for the same time period.
"We are tracking some of the warmest temps we've seen in years," ABC7 Meteorologist Cheryl Scott said.
High temperatures on Thursday will reach the mid-90s. Heat indices on both days will exceed 100 degrees, with a maximum of 115 degrees.
Counties under the Excessive Heat Warning include Cook, Will, DuPage, Lake, McHenry, Kane, Kankakee, Grundy, Kendall, LaSalle, DeKalb, Iroquois, Ford, Livingston, Winnebago, Boone, Ogle and Lee.
Residents are urged to plan ahead, have a cool place to take shelter, avoid outdoor activity during the afternoon, drink plenty of fluids and check on relatives and neighbors.
Metra is already warning riders that there could be delays due to the heat later this week. Any time temperatures exceed 95 degrees, Metra said it may be necessary for trains to reduce speeds to compensate for heat-related stress on tracks and signals. The slower speeds could mean delays up to 10-15 minutes, Metra said.
Watch the latest forecast from the First Alert Weather Team:
COOLING CENTERS OPEN ACROSS CHICAGO
Cooling centers are open across Cook County, and the City of Chicago also operates six cooling centers during the summer months. The Garfield Center, located at 10 S. Kedzie, is available 24 hours a day, seven days a week to connect residents to emergency shelter.
The following cooling centers are open from 9 a.m. to 5 p.m. Monday through Friday:
Berwyn Library, 2700 S. Harlem, Berwyn;
Berwyn Police Department, 6401 W. 31st, Berwyn;
Bloom Township Village Building, 425 S. Halsted, Chicago Heights;
Bremen Township Community Cneter, 15350 S. Oak Park, Oak Forest;
Bremen Township Administrative Office, 16361 S. Kedzie Pkwy. Markham;
Calumet Township Community Center, 12633 Ashland, Calumet Park;
Cicero Village Building, 4949 W. Cermak, Cicero;
Cicero Police Office, 4901 W. Cermak, Cicero;
Cicero Public Safety Building, 5410 W. 34th St., Cicero;
Cicero Community Center, 2250 S. 49th Ave., Cicero;
Elk Grove Township, 2400 S. Arlington Hts., Arlingotn Heights;
Hanover Township, 240 S. Illinois Rt. 59, Bartlett;
Leyden Township, 2620 N. Mannheim, Franklin Park;
Lyons Township, 6404 W. Joliet Rd., Countryside;
Maine Township, 1700 Ballard Rd., Park Ridge;
Niles Township, 5255 Main St., Skokie;
Norwood Park, 7833 W. Lawrence, Norridge;
Oak Park, 130 S. Oak Park Ave., Oak Park;
Orland Township, 14807 Ravinia Ave., Orland Park;
Palatine Township, 721 S. Quentin Rd., Palatine;
Palos Township, 10802 S. Roberts Rd., Palos Hills;
Proviso Township, 4565 Harrison St., Hillside;
Riverside Township, 47 Riverside Rd., Riverside;
Stickney Township, 7745 S. Leamington, Burbank;
Barrington Public Safety Building, 400 N. Northwest Hwy., Barrington;
Barrington Train Station, 201 S. Spring St., Barrington;
Wheeling Township, 1616 N. Arlington Heights Rd., Arlington Heights; and
Worth Township, 11601 S. Pulaski Rd., Alsip.
Residents are advised to contact the cooling center first to make sure it is open.
FULL LIST: Cook County cooling centers
"Temperatures this high could lead to heat-related illnesses with prolonged exposure," the weather service warned. "The elderly, small children and pets are especially susceptible."
Central US bracing for 'heat dome;' heat indexes to top 100
This map says it all. Stay safe as it heats up: Drink water, stay out of the sun, and check on your neighbors. pic.twitter.com/c1qFTmq2IV— President Obama (@POTUS) July 20, 2016
High temperatures and humidity will bake much of the central U.S. this week, sending heat indexes soaring as high as 115 degrees in some places for the first time this year.
The National Weather Service says the high pressure system, sometimes called a "heat dome," will push conditions to their hottest point this summer, though temperatures will stay short of records. Authorities from Minnesota to Louisiana are warning people to take precautions and check on the elderly and other vulnerable neighbors and relatives.
Officials blamed heat for the death last week of an elderly woman in St. Louis County, Missouri. In Illinois, a 4-year-old girl was hospitalized Tuesday after being found unresponsive in a hot vehicle in a northwest Chicago suburb. Details on her condition have not been released.
The Sun-Times Media Wire and Associated Press contributed to this report.