UPDATED 07/05/12 4:17 p.m.
CHICAGO (CBS) -- Chicago broke a 101-year-old heat record by midday on Thursday – and authorities determined that the heat has been responsible for two deaths.
The temperature at O'Hare International Airport hit 103 degrees at 2 p.m., breaking the July 5 record of 102 set in 1911. While O'Hare is the official site for record-keeping, Midway Airport recorded a temp of 105 at 1:30 p.m.
Shortly after that, a brief thunderstorm dropped the temps to the mid-80s at O'Hare, essentially ruling out a shot at the all-time record. But even that cool-off didn't last long. By 3:51 p.m., the temperature was back up to 97 at O'Hare.
LISTEN: WBBM Newsradio's Nancy Harty reports
CBS 2 Meteorologist Ed Curran says Chicago also tied a record dating from 1911 for the 4th of July on Wednesday – with a high of 102 degrees.
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The forecast high for Friday is hotter still at 104. That's one degree shy of the hottest day ever recorded officially in Chicago. Chicago hasn't had three days of 100+ degrees since July 3-5, 1911
The National Weather Service says heat indexes could peak at 118 degrees.
The city remains under an excessive heat warning until 10 p.m. Friday. The NWS advises minimizing time outside, wearing loose-fitting clothing, drinking plenty of water, and scheduling frequent rest breaks.
On top of all that, an air quality alert is in effect through Thursday night for Northern Illinois and Northwest Indiana. Increased ozone levels will make stress on the body even worse, particularly for the very young or elderly and those with existing respiratory problems.
The Cook County Medical Examiner's office said the ongoing heat wave is responsible for two deaths.
Eugene Burns, 56, of 1205 S. 4th Ave. in Maywood was pronounced dead at 8:02 p.m. Wednesday at Loyola University Medical Center in Maywood, according to the Cook County Medical Examiner's office. An autopsy Thursday found he died of heart disease with obesity and heat stress as contributing factors.
Jon McCullough, 48, of 2317 W. Ainsle St., was pronounced dead at Swedish Covenant Hospital at 1:57 a.m. Thursday, the medical examiner's office said. An autopsy Thursday found also died of heart disease, with obesity and heat stress contributing factors.
A third recent death might also be due to the heat. Iona Kendrick, 95, died Tuesday night at her home in the 9300 block of South Green Street, and while her autopsy has been deemed inconclusive, pending further studies, the Cook County Medical Examiner's office says her death may have been heat-related.
In addition, at least 232 people have been taken to area hospitals in Chicago so far because of the heat.
Loyola University Medical Center in Maywood reports seven cases of heat-related illnesses. The patients were treated and released for conditions such as asthma and sunburn.
Ten heat-related patients were reported at Northwestern Memorial Hospital.
But regardless of the dangers, CBS 2's Susanna Song reports some people have no choice but to brave the heat.
Felipe Igurra of Kinsella Landscape told CBS 2 in Spanish that if he has no choice to work in the heat, or else he won't get paid. So it doesn't matter how unbearably hot it gets, or how much the workers sweat.
"I'm drinking the water – a lot of water," said co-worker Efram Magana.
Water is also something some drivers are keeping around for themselves, and for their elderly clients. They work for one of the city's vendors to deliver food, and they're the eyes and ears for the city.
"Just yesterday, I had to make a call. A lady, 95 years old, she says, 'Is my air conditioning working?' I said, 'No ma'am, it's not on," said driver Derrick Coleman. "So I made a call, they made a call to Human Services."
Lueretha Chambers was preparing to deliver another load of meals Thursday, but she's says there is a bigger responsibility.
"Today, I'm looking for signs of fatigue, you know, asking them are they OK? A lot of them are nauseous and, 'Do you have a headache, what's going on?'" Chambers said.
On Wednesday on her route, Chambers found a man passed out on the ground.
"He's on the floor, and he be laying out there for a while, and it's so hot, and I said, 'Baby, you've got central air. Why don't you go back in the house?" Chambers said.
Many of the senior citizens with whom Chambers interacts can't feel the heat even when the temperatures get up to the triple digits.
"I have quite a few clients that are taking blood thinners, and they really think it's cold to them," Chambers said. "Baby, it feels like a sauna in the house."
City officials are taking the heat wave very seriously, particularly due to the risk of heat exhaustion and heat stroke.
Some of the symptoms of heat exhaustion include heavy sweating, paleness, muscle cramps, a fast and weak pulse and fast and shallow breathing.
Untreated heat exhaustion can lead to heat stroke, which is defined by a body temperature of more than 105.1 degrees. Someone suffering from heat stroke may suffer from dry skin, a rapid pulse, dizziness, fatigue, seizure, and hallucinations.
And as CBS 2's Susanna Song reports, physical signs of the toll taken by the heat abound across the city. Most notably, a huge section of pavement on Columbus Drive in Grant Park buckled around 3:30 p.m. Wednesday in the scorching heat.
With temperatures topping 100 degrees, pavement cracked and rose 2 to 3 feet into the air, prompting authorities to close Columbus Drive between Balbo Drive and Roosevelt Road.
Anyone who takes Columbus Drive to work will have to avoid it Thursday morning.
As it happens, officials were planning to close the affected stretch of Columbus Drive anyway due to the Taste of Chicago as they begin setup for the festival.
But now, cars really cannot even get through.
Chicago Department of Transportation Commissioner Gabe Klein said the buckle will take time to repair.
"We're talking our time with this project, because it was going to be closed anyway for the Taste of Chicago," Klein told WBBM Newsradio's Nancy Harty. "We'd like to have something in place by tomorrow, at least in terms of at least a temporary fix."
But crews cannot pour concrete on Thursday, with the heat index dangerously hot, Klein said.
No one was injured in the pavement buckling.
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