The record high for July 6 in Chicago was 99 degrees, which was set in 1988.
City officials are urging Chicago residents to check on their neighbors and families, the elderly and the disabled. Chicagoans can call 3-1-1 to find nearby cooling centers.
The city's emergency management agency says from June 28 through the Fourth of July, the total number of heat-related calls to 9-1-1 was 307.
The Chicago Fire Department transported 310 patients for heat-related problems during the same period. And the total number of well-being checks completed by the Department of Family and Support Services was 159.
Copyright 2012 The Associated Press.