The mercury climbed to 103, shattering the previous daily record of 99 degrees.
This week's heat has been dangerous. On Friday, four more deaths related to the heat have been confirmed, making it a total of six people who have died during this current heat wave.
The victims range in age from 48 to 91. All had heart conditions aggravated by the heat. One of the victims lived on the second floor of a building in Ukrainian village. Authorities say Carmen Mercado, 81, was found dead yesterday by her daughter. She lived, neighbors say, with no air conditioning.
"I don't know. You wish you could have known and helped them out in some way, but what are you going to do, you know?" said neighbor Yaniv Schiff.
A mile and a half away, Riley Kimble, 59, was found dead in a single room occupancy building. Like the other five heat victims, Kimble's death was heart-related, with heat playing a role.
Though it's unclear if he had air conditioning, residents here say many cannot afford it because it raises the rent $20 a month.
"It's like an oven. It's like being in a microwave or something," said a resident named Gregory, describing what it is like being inside with no air conditioning.
These scorching conditions are made worse by the so-called heat island effect, in which streets and buildings trap heat, contributing to a lack of cooling at night.
At 5 p.m., the pavement was 123 degrees, according to our thermometer, which measures temperature using a laser. At 9 p.m., the pavement was still a sizzling 103. It can take a steady toll on the body.
"All this adds up, and if it adds up and you haven't been taking good care of yourself in the last three, four days, all of a sudden you can hit a point where it's hitting you pretty hard, and you're having pretty serious effects to the heat," said Dr. Louis Hondros with Rush University Medical Center.
Friday night, Chicago police and fire have been responding to numerous reports of blown transformers. In the last three days, the city says it has had to cap nearly a thousand fire hydrants that have been forced open.
Friday night, folks in Little Italy were finding more constructive ways to stay cool.
"I'll be melting without it," said Alfred Perez, who had just gotten some Italian Ice. "I have to get the Italian Ice."
ComEd has not been able say how many people were in the dark Friday night. They did say that usage has recently been about 50 percent higher than normal for this time in July.
At the 21st annual Chicago Tribune North Michigan Avenue Arts Festival on Friday, the crowd was rather thin amid the heat wave. The art festival goes through the weekend.
Rain, sleet, and snow are wishful thinking. Nine years as a mail carrier, and Maisha Bell-Norman says this is the worst.
"It's pretty warm this week - it has been pretty exhausting every day on a daily basis dealing with this 100 degrees, 93 degrees, 95, it's rough on us," said Bell-Norman.
The weather is weighing on those who work outside, but some are even busier with the extreme heat. Mr. Duct Heating and Air Conditioning had dozens of calls Thursday and they are booked through 8 p.m.
"We haven't slept. The phones have been ringing nonstop," said Mr. Duct's Jason Heller.
More Chicagoans have central air conditioning these days. The U.S. census reports 69 percent have central air compared to 1995, when 49 percent of Chicago homes had central air.
Residents of the CHA senior building Las Americas have air conditioning units, but the tenant patrol has been doing three daily checks since the temperatures have been so high.
The fellow tenants check the temperatures in the units and makes sure the residents have water and seem in good health.
"I used to work with them, I used to be a tenant patrol too, that means I know always checking on us is so important," said Arminda Gomez.
An excessive heat warning is in effect through Saturday afternoon for much of the Chicago area. That's when a cooler front is expected to move in. The excessive heat warning lasts until 4 p.m. Saturday for Cook, Lake, Kane, McHenry, DuPage, and Kane counties in Illinois and Lake and Porter counties in Indiana. It remains in effect until 7 p.m. Saturday for LaSalle, Grundy, Will and Livingston County.
City health officials warn that extreme heat and humidity are more than an inconvenience. They can be dangerous and even deadly.
The people at greatest risk for heat related illness are the elderly and children under the age of four.
Conditions such as obesity, heart disease, poor circulation, and dehydration can limit the body's ability to regulate its temperature.
So people are advised to keep cool. The best way to do that is to be in an air conditioned building.
"Even a few hours spent in air conditioning can help your body stay cooler when you go back out into the heat," said Dr. Suzet McKinney of the Chicago Department of Public Health. "Electric fans will provide some comfort, but when the temperature is in the high 90's fans will not prevent heat related illness."
McKinney went on to say very hot temperatures may damage the brain and other vital organs, so it is important to know the signs of heat exhaustion and heat stroke.
Pets also can be affected by hot weather
Amid this extreme heat, there are steps you can take to keep your pets safe.
The staff at the Wicker Park Veterinary Clinic does not see many heat emergencies. When they do, Dr. Jacob Cohen describes them as dramatic and life threatening.
He recommends limiting your pets' exercise to the early morning or late evening hours.
"It's very important to keep your pets cool. They don't know what's too much, so make sure you're keeping them indoors, keeping them in the air conditioning if you can. If you can't do that, maybe wet them down," said Cohen.
Signs that your pet may be suffering the effects of the heat include excessive panting and dark red gums instead of the usual pink.