The temperature could be well into the 90s by the end of the weekend.
For those who've been without electricity for most of the week, the power is finally coming back on just in time to fire up the air conditioning.
ComEd reported that about 15,000 customers remained in the dark Friday evening, most of them in the north suburbs. ComEd says all of those customers should have power back by midnight Friday night.
At the height of the outage, more than 850,000 customers were without power.
Dorfler's Meat Market in Buffalo Grove has been without power since Monday. Employees are waiting anxiously for the power to come back. Manager Dale Badgerow says ComEd keeps telling him the market will be back on line soon.
"Every time that we talk to them, it's either noon that day or midnight that night, for sure we're going to have you back up and running," said Manager Dale Badgerow.
In business since 1978, the meat market, freezers and deli are empty. The business says the power outage has cost more than $50,000. Vendors have loaned the market freezer trucks to store the meat but that can only last so long, especially with the high temperatures expected on Sunday.
"The heat if going to do nothing but warm up those trucks. Generator are going to work harder and we need our power to go on," said Badgerow.
Also in Buffalo Grove, Shalom Kosher Bakery is without power. It went back on for a day but went off again. Owner Migoal Benezra supplies businesses and summer camps throughout metro Chicago to the Wisconsin Dells and has not been able to fulfill orders.
"It is not just losing the money but the relation between me and the customer," said Benezra.
"All of our crews, all of our leadership, really all-hands-on-deck effort to get the remaining customers put back in service by midnight tonight," said Fidel Marquez of ComEd.
ComEd's promises are not helping 85 residents that live in Country Club Estates in Long Grove. They have been without power since Monday. Power came on Wednesday but went out the next day.
"You can't flush your toilet. You can't turn on your lights. You can't cook if you don't have gas, you have electric. It's a mess," said Cindy Horowitz, Long Grove resident.
News of the heat wave expected to hit the Chicago area is worrying some residents without power.
"I bought more ice and bottled water, but I have a lot of food rotting and I am not sure what to do about that," said Karen Mendez, Long Grove resident.