As Chicago Public Schools students return to class Monday, the heat index is expected to exceed 100 degrees.
The National Weather Service in Chicago issued an excessive heat warning Monday afternoon through Tuesday night due to “dangerously hot and humid conditions.” The city is opening cooling centers and urging Chicagoans to stay indoors when possible.
In a statement Sunday, CPS said it had canceled all outdoor activities or moved them indoors and assured parents that all classrooms were air-conditioned and the temperature would be maintained at a comfortable level. Procedures are in place in the event of a cooling system malfunction, the statement said.
The Chicago Teachers Union also released a statement Sunday.
The CTU said it is negotiating with CPS to get better cooling systems because many of the city’s older school buildings are not equipped to handle the extreme heat. The union said it was disappointed the problem wasn’t fixed before the start of the school year, but expressed confidence CPS would be able to handle this week’s heat wave.
“A city that can host an unprecedented convention with thousands of visitors can surely make the first day of school safe and successful,” the CTU statement said, referring to last week’s Democratic National Convention.
Heat index values could reach 107 degrees on Monday and 110 degrees on Tuesday. Meanwhile, nighttime temperatures are only expected to drop to 70 degrees.
The expected extreme heat comes after the Illinois Environmental Protection Agency declared Sunday an Air Pollution Action Day for Chicago-area counties due to elevated ozone levels, caused by pollutants emitted by cars, industrial sources and wildfires such as those currently raging in Canada.
It’s not uncommon for poor air quality and heat waves to occur together, as particles linger in stagnant masses of warm air, meteorologist Casey Sullivan said.
Climate change is making the Chicago area wetter, which increases the perceived temperature, or heat index, and makes nights warmer. Average precipitation increased 15% in Illinois between 1895 and 2019. As a result, average summer temperatures have increased 1.5 degrees over the past six decades, with average minimum temperatures increasing 2.2 degrees.
Heat becomes dangerous if it persists for more than a day, and hot nights after hot days don’t give the body enough time to cool down, according to the National Weather Service.
Heat doesn’t affect everyone equally in Chicago, either. According to a 2023 study sponsored by the city, dense residential and industrial areas retain more heat than communities near natural, open spaces like the lakefront. Temperatures measured in different neighborhoods at the same time of day varied by as much as 72 degrees. Those results didn’t account for humidity, which increases the heat index, meaning the temperature gap likely seemed even wider.
Air quality on Sunday was unhealthy for sensitive groups, including people with asthma, children and the elderly, and they were advised to avoid prolonged outdoor activity.
During the heat wave, the National Weather Service and the City of Chicago are encouraging residents to drink plenty of water and use air conditioning. Children and pets should never be left unattended in a vehicle for long periods of time, as this week’s extreme heat can cause temperatures inside cars to soar in minutes.
Even though schools are limiting time spent outdoors, parents are advised to send their students to school with loose clothing and full water bottles.
Public cooling centers, which include libraries, park facilities and community college buildings, will be open to provide relief from the heat. Click here for a full list of locations and hours.
Scattered thunderstorms Tuesday night and Wednesday are expected to cool the city by midweek.
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