UPDATED 07/12/11 9:44 p.m.

MOUNT PROSPECT, Ill. (CBS) — About 250,000 ComEd customers were still without power as of Tuesday night, a day after a powerful storm slammed the Chicago area, and officials said some customers might not have power back until Saturday.

Originally, ComEd said that a record 868,000 customers were without power at the peak of outages after the storm, but Tuesday afternoon officials revised their estimate to about 850,000 customers, just short of a record set in 1998.

As of Tuesday afternoon, 900 crews were out to restore power. As of 9 p.m., there were still about 250,000 ComEd customers without power. More than 631,000 customers have had power restored since the start of the storm, according to ComEd.

ComEd officials said that 75 percent of their customers affected by the storm should have power restored by Wednesday night. About 90 percent should have their power restored by the end of the day Thursday or early Friday. All remaining customers should have power back by late Friday or on Saturday.

Among the most significant outages are the lights along U.S. 41 in Gurnee and Wadsworth, and Routes 137 and 22 near the Tri-State Tollway, CBS 2’s Derrick Young reports.

Newsradio 780’s Steve Miller reports, Gurnee residents don’t recall a power outage like this before. First Street and Old Grand Avenue is closed due to downed power lines.

The owner of the nearby Gurnee Funeral Home believes that his business won’t have power until Friday.

LISTEN: Newsradio 780’s Steve Miller Reports

“We have restored power to more than half a million customers who were affected by yesterday’s storm,” ComEd spokesman Tony Hernandez said. “I have to tell you, it was one of the worst storms that we’ve seen in past 13 years.”

Because of the severity of the damage caused by the storm, full restoration could take several days, Hernandez said. Customers can get updates by calling (800) EDISON-1, going to ComEd.com, or finding ComEd on Twitter.

Within the past month, residents of Mount Prospect have already been through a tornado, which was followed by widespread power outages that in some days took days to fix. Now, as CBS 2’s Susanna Song reports, many are in the dark – and the heat – once again, following a short, but very violent storm on Monday.

Just as they did after the tornadic storms on June 21, the Monday storms left the even-numbered side of Pine Street without power, while power remained on the odd-numbered side.

Julie Filipic lives on the even-numbered side, and she has been without power since the storms rolled through on Monday morning.

“Without electricity in this kind of weather, we don’t have air conditioning, and we pretty much can’t use anything – our appliances, or anything else in the house,” she said.

Filipic said this outage is even worse than the one last month, given that temperatures are considerably hotter, and power was out all through the day Monday because the storms struck early in the morning.

“Last month, we were out for 15 hours, Filipic said. “Today, so far, it’s been longer than that, since yesterday morning.”

Also last time, Filipic said: “Most of the power outage was overnight, so we were sleeping during the power outage. Yesterday, it was all day long and it was 90 degrees.”

Filipic and her children spent the day Monday going out to lunch and cooking on the grill for dinner, then going to the library to stay cool and use the Internet. One of Filipic’s daughters went to Starbucks, while her son went to a couple of friends’ houses who still had power.

“We kind of just hung out in the basement while we were at home, where it was the coolest,” she said.

Coming down Pine Street, one will notice extension cords running from one side of the street to the other.

“We’ve lived on this block for 11 years, so we already know each other pretty well, and when the storm hit in June, everybody just kind of came out to see what they could do, and we realized we needed power, so everybody just started collecting extension cords, and hooking up to the houses that had power,” Filipic said.

The extension cord running across the street has provided power for Filipic’s refrigerator and sump pump, as well as a fan that is plugged into a surge protector.

“I just walked outside, and Julie said: ‘We’re out again. Do you mind if we borrow?’ And I said, ‘Sure, no problem. Let’s get you hooked up,’” said the Jill Burgos, Filipic’s neighbor across the street who still has power.

Burgos hooked up the extension cord from Filipic’s house to an outdoor outlet that is used for Christmas lights during the winter.

“It’s really easy. It’s not a lot of effort. It’s not a lot of electricity use,” Burgos said. “Really, it’s just their refrigerators so they don’t lose their food, which could cost hundreds of dollars.”

LISTEN: Newsradio 780’s Bernie Tafoya reports

Libertyville was also hit particularly hard. Resident Jeff Johnson told WBBM Newsradio 780’s Bernie Tafoya he was not thrilled by the news that it could be a few days before he has power back.

“I’m not happy to hear that,” Johnson said. “I’ll be looking for a place to take a shower today.”

Evanston was also hit with 18,745 outages, which had been reduced to 8,300 by Tuesday morning.

Still, given the several days it make take to restore power to everyone, the City of Evanston has opened its community centers and libraries, and the Morton Civic Center at 2100 Ridge Ave., as cooling centers. Several facilities also have wi-fi connections.

The power outages also forced the Internal Revenue Service in Downers Grove to close for the day on Tuesday. The IRS directed those in need of taxpayer assistance to visit offices in downtown Chicago, Orland Park or Schiller Park, call the IRS helpline at (800) 829-1040, or visit the IRS Web site, in lieu of the Downers Grove office at 2001 Butterfield Rd.

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