Chicago’s low temperature Sunday was a stifling 80 degrees, breaking the June 22 record for minimum temperature.
The low was 4 degrees higher than the previous record set in 1923, according to the National Weather Service.
Sunday’s record comes after the June 21 record for minimum temperature was toppled Saturday night, with the temperature dropping to just 78 degrees. That’s also 4 degrees higher than the previous record set in 1923.
“The longevity of the heat episode is definitely a concerning aspect to this,” said Lee Carlaw, a meteorologist for the NWS.
An extreme heat warning remained in effect across Cook County through Monday night. Through the rest of the week, Chicago is in store for scattered afternoon and evening thunderstorms, Carlaw said.
Human-made climate change is making summers in the Midwest more humid overall, even as seasonal highs have rarely broken records in recent years. According to experts, sweltering summer nights, in particular, have become more common. In Chicago, overall summer average temperatures have warmed by 1.7 degrees between 1970 and 2024. Average lows on summer nights have increased by 2.5 degrees in that same time.
Moist heat that persists over a long stretch can be particularly dangerous without access to air conditioning.
On Sunday, the weather service reported sunny conditions with a high temperature near 96 degrees and a heat index value, which is essentially how hot it actually feels, as high as 101. By nighttime, the low temperature will drop to 80 degrees with wind gusts up to 35 mph. The heat index will likely remain in the 90s late into the evening hours.
Temperatures in Chicago remain warmer overnight due to a phenomenon called the “urban heat island effect.” Concrete and asphalt radiate heat absorbed during the day, making urban areas typically several degrees warmer than rural areas, the weather service said.
Higher nighttime temperatures can lead to insufficient or poor, restless sleep, which can compromise the immune system, increase the risk for cardiovascular disease and diminish cognitive performance. Heat-related illnesses like heat stroke, which occurs when the body can no longer control its temperature, can also be fatal.
Carlaw warned of a rapid increase in heat-related illnesses, particularly for the elderly and those with pre-existing medical conditions. He recommended wearing lightweight and loose-fitting clothing outside and limiting strenuous activities to the early morning or evening. Staying in air conditioning as much as possible is best.
“If you have to be outside, ensure that you’re taking frequent breaks, drinking plenty of water,” Carlaw said. “If you are aware of vulnerable populations, ensure that you’re checking in on them from time to time.”
Pets also shouldn’t go outside for long walks during the middle of the day, and should have access to plenty of water, the weather service added.
While it may be a bit earlier than usual in the summer, Carlaw said it’s normal for Chicago to experience this type of heat wave one or two times during the season. He said the record high for June 22 was 97 degrees, set in 1988.
“It is not entirely unusual,” he said. “We’re not strangers to hot and humid conditions up here.”
Many of the city buildings that operate as cooling shelters aren’t open on the weekend, but residents can step inside public libraries, City Colleges of Chicago campus locations, Chicago Park District field houses and splash pads during their hours of operation for relief, the city said in a news release. The Garfield Community Service Center is also open Sunday from 9 a.m. to 5 p.m.
Heat wave’s high humidity raises health risks in Chicago and across the country
Over the last three years, the city recorded 485 heat-related deaths and more than 700 heat-related emergency room visits in Chicago, Public Health Commissioner Olusimbo Ige said at a Friday news conference. Public health data shows the 60620, 60623, 60628 and 60651 ZIP codes historically see more heat-related emergencies than other locations, Ige added.
By Saturday afternoon around 3 p.m., the heat index reached 103 degrees in Chicago and 107 degrees in Aurora. At Kathy Osterman Beach in the Edgewater neighborhood, dozens of Chicagoans lounged on the sand and dipped their toes in the water.
Friends Lyndee Boyce and Chloe Wesley, both from the Lakeview neighborhood, chose to stay cool by swimming during the hottest part of the day. They said they avoided the direct sunlight so as not to get too sunburnt and recommended bringing lots of sunscreen.
“It’s kind of the first nice day out in a while,” Wesley said. “I just wanted to lay in the water.”
Chicago Tribune’s Adriana Pérez contributed.
