Temperatures at Midway Airport reached 100 degrees for the first time in a decade Tuesday as a heat wave belted the Chicago area, according to the National Weather Service.

City leaders who gathered Tuesday morning to offer suggestions on how residents could stay safe during the heat wave recommended staying cool and drinking plenty of water.

The extreme heat prompted the National Weather Service to issue an “excessive heat warning” in northern Illinois that expires Wednesday evening.

By 3 p.m. Tuesday, temperatures at Midway had reached 100 degrees. It was the first time since July 2012 that the airport reached that mark, the weather service said. At O’Hare Airport, temperatures climbed to 96 degrees around 2 p.m., falling a few degrees shy of the record high for June 14 of 99 degrees set in 1987. Official temperature records for the city are measured at O’Hare.

Anyone seeking a cool place should go to a city library, park district field house or one of the city’s six cooling centers.

Rich Guidice, head of the city’s Office of Emergency Management and Communications, offered this advice for those who do not have air conditioning: keep shades drawn with windows slightly open, keep electric lights off or turned down, minimize the use of ovens of and stoves, wear loose, light cotton clothing and take cool baths and showers.

Residents should not leave anyone, including pets, in a parked car — even for a few minutes, Guidice said during a news conference at OEMC headquarters in the West Loop.

“Do not underestimate the health risks of heat and humidity, they are dangerous and, in some cases, can be deadly,” said Dr. Jennifer Seo, chief medical officer for the Chicago Department of Public Health.

Residents were also encouraged to check on relatives, neighbors and vulnerable populations. If someone can’t be reached, people are encouraged to call 311 to request a well-being check, and of course, to call 911 if someone is experiencing a medical emergency.

Matthew Beaudet, head of the Department of Buildings, said that building owners and managers have been asked to make sure all their cooling equipment is operating properly.

Beaudet said members of his department has visited senior buildings to make sure equipment is functioning properly and if there are mechanical issues, they are “addressed swiftly.”

The city will be operating six cooling areas to allow residents to get out of the heat, according to the Office of Emergency Management and Communications.

These cooling areas are open from 9 a.m. to 5 p.m Monday through Friday (except for the Garfield Center, which will be open 24 hours):

• Englewood Center, 1140 W. 79th St.
• Garfield Center, 10 S. Kedzie Ave.
• King Center, 4314 S. Cottage Grove Ave.
• North Area Center, 845 W. Wilson Ave.
• South Chicago Center, 8650 S. Commercial Ave.
• Trina Davila Center, 4312 W. North Ave.

Residents can also find relief in one of the city’s more than 75 Chicago Public Library locations and more than 250 Chicago Park District field houses as well as 176 splash pads.

Lakefront beaches are also open. Park District pools will open later this month.

People should be aware of the symptoms of heat exhaustion, a milder form of heat-related illness that can develop after several days of exposure to high temperatures and inadequate or unbalanced replacement of fluids. Heatstroke is more serious and occurs when the body starts to lose its ability to regulate itself.

The telltale signs of heatstroke:

• An extremely high body temperature, such as 103 degrees or above
• Dizziness and nausea
• A throbbing headache and a pulse that is rapid and strong
• Skin that is red, hot and dry

A cold front will bring relief later this week. By Thursday, high temperatures will be in the low 90s, and Friday will be in the mid-80s. It could feel more like the 70s near Lake Michigan.

The weekend is forecast to be sunny with highs in the 80s.