Commonwealth Edison said Tuesday it hopes to have 75 percent of the customers who were knocked out by Monday's storms back online by Wednesday.
About 900 crews worked through the night to restore service to more than 500,000 customers after the fast-moving storms left 868,000 homes in the dark, the biggest outage in about 15 years.
Crews from Indiana, Michigan and Wisconsin are lending a hand as about 369,000 residences remain without power, including 207,000 in the northern region, which was hit the hardest.
"I am committed to having 90 percent of our customer base back by end-of-day Thursday, not later than the early hours of Friday," said ComEd Chairman and CEO Frank Clark during a Tuesday afternoon press conference.
The lack of electricity is a big problem for families trying to stay cool in hot, humid weather with highs of 86.
The American Red Cross opened shelters Monday evening in Chicago for those displaced by the storm or in need of an air conditioned place to stay. Call 312-907-0520 for locations.
Area Home Depot stores also are open for the next 24 hours with generators in stock.
There's a waiting list, but chain representatives say plenty are available at the following local stores: 2201 Oakton St. in Evanston, 6625 Grand Ave. in Gurnee, 3200 West Route 60 in Mundelein and 2050 Route 83 in Round Lake Beach.
Meanwhile, Chicago Streets and Sanitation continue work to clean up 2,500 reported down trees, including more than 60 trees blocking streets. About 350 tree emergencies have been relieved, according to Streets and San Commissioner Tom Byrne.
Trees and power lines are down across the city and suburbs. In McHenry, fallen power lines burst into flames, starting a fire along the side of the road at Ridge Road.
In Wilmette, storms ripped out the town's oldest living tree by its roots. The bicentennial ash tree had stood there since 1746. Residents showed up to take photos of the tree and even take parts of it home with them.
Crews said it will take a week to clean up damage from the storm.