Updated story

Chicago city officials urged caution Thursday as the city was in the sweltering midst of what could be its hottest day in seven years.

Thursday was expected to bring triple-digit temperatures to the Chicagoland area. And while the temperature at the O'Hare International Airport only hit 93 degrees by noon, it still remained possible, if less likely, that the temperature there could still reach 100 for the first time since 2005, the Chicago Tribune reports.

By mid-afternoon Thursday, the temperature at Midway Airport hit 100, while O'Hare hit 99, two degrees shy of the day's record high.

The National Weather Service issued a heat advisory for the area lasting from noon to 8 p.m. and the city is telling Chicago residents to be cautious as highs could still reach between 96 and 101. Humidity could make it feel as hot as 108 outside, NBC Chicago reports.

"I want to state in the clearest terms that extreme heat and humidity are not just an inconvenience, they are dangerous and can be deadly,” Dr. Julie Morita, Chicago Department of Public Health deputy commissioner told the Chicago Sun-Times.

Residents are urged to remain indoors if possible, to take care of their neighbors and pets and to stay hydrated. Chicagoans without air conditioning are urged to go to a cooling center -- such as a public library or police station. Illinois residents may click here to find the cooling center located nearest to them.

Some Chicago Public Schools canceled their Thursday summer classes because their schools are not equipped with air conditioning, according to ABC Chicago.

In advance of the balmy day, the city warned residents against opening fire hydrants as a means to keep cool, WBEZ reports, and ComEd has said it has 300 additional crew prepared to work extended or overnight hours in the event of any power outages in the area, according to Fox Chicago.