Northern Illinois experienced an intense heat wave during the first week of July.  High temperatures at Chicago O'Hare Airport reached 102 on the 4th, 103 on the 5th and 6th and 98 on the 7th.  Low temperatures remained in the upper 70s to lower 80s during much of the heat wave with a low temperature of just 82 degrees on the morning of the 6th.  Maximum heat index values were mostly in the range of 105 to 115 each day across northeast Illinois. A cold front moved across the area during the late morning and early afternoon of July 7th, bringing several days of near normal temperatures for mid July.
Between July 4th and July 11th, the intense heat was a direct or contributing factor to at least 23 deaths in Cook County.
On July 4th, heat caused Columbus Drive, just north of Roosevelt Road, to buckle.  The damage stretched across the entire street, just above an underground pedestrian walkway.
On July 4th, heat caused the railroad lines on a bridge over Shermer Road in Glenview to expand leading to a train derailment.  A total of 28 freight cars piled up leading to a collapse of the bridge.  Two people in a car driving under the bridge were killed.

Excessive Heat in LA SALLE, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in LAKE, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in LEE, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in LIVINGSTON, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in MCHENRY, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in OGLE, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in BOONE, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in COOK, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 750.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in DE KALB, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in DU PAGE, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in IROQUOIS, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in FORD, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in GRUNDY, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in KANE, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in KANKAKEE, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in KENDALL, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in WILL, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Excessive Heat in WINNEBAGO, ILLINOIS
From 04-JUL-12 12:00:00 to 07-JUL-12 18:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations