Air Quality Alert and Severe Storms in Chicago
Air quality in the Chicago area remains poor for the third straight day in a row, with an air quality alert in effect through Wednesday night, along with extremely muggy conditions and the chance for severe storms, the NBC 5 Storm Team said.
According to the National Weather Service, the alert was issued for Lake, McHenry, Kane, DuPage, central Cook, Kendall, Grundy and northern Will Counties in Illinois. In Indiana, it was issued for Lake, Porter, northern LaPorte and Newton Counties.
Air Quality Index
As of 5:45 a.m., Chicago’s air quality index was ranking in the “good” category, according to AirNow.gov, but it was expected to worsen as the day goes on. NBC 5 Storm Team Meteorologist Kevin Jeanes noted Wednesday’s air quality alert was mostly due to high levels of ozone — which occurs when sunlight reacts with pollution — rather than smoke from Canadian wildfires.
Heat and Humidity
The alert comes as heat and humidity across Chicago rise, with dew points in the low 70s. Such high dew points will make the muggy conditions feel in the “miserable,” category, NBC 5 Storm Team Meteorologist Alicia Roman said.
“With that humidity in place, it could feel more like the mid 90s to 100,” Roman said, though high temperatures would only remain in the mid 80s to low 90s.
Jeanes added that air quality alerts due to high levels of ozone are common with these “hot, summer days.”
Severe Storms Possible
Wednesday also sees the chance for strong to severe storms to develop, Roman said, beginning around 2 p.m. in counties to the north and west. Those storms will track across northern Illinois and into northwest Indiana through 8 p.m., the NWS said, with storms hitting Chicago around 5 p.m.
Wednesday’s storm threat puts the entire Chicago area at a “slight” risk for severe weather, which ranks as level two of five. The strongest storms will be capable of producing damaging winds as high as 60 miles per hour, and torrential downpours leading to localized flash flooding, Roman said.
“And a tornado cannot be ruled out,” the NWS warned, along with “frequent cloud-to-ground lightning.”
Thunderstorms are expected to develop in the early to mid-afternoon, then track across northern Illinois and into northwest Indiana. A few of the storms may become severe, with locally damaging winds the primary threat. #ilwx #inwx pic.twitter.com/KWAigWGzxE
— NWS Chicago (@NWSChicago) July 16, 2025
Forecast for the Rest of the Week
Showers were possible again Thursday at times, Roman said. A big temperature drop was also in the forecast Thursday, with highs only in the 70s.
Lower humidity and temperatures in the 70s and 80s will continue into Friday, Roman said. But Friday night through the weekend, “periodic bouts of showers and thunderstorms” were expected, the NWS said.
“Any storm during this period may be severe with damaging winds and flash flooding,” a hazardous weather outlook from the NWS said.
Conclusion
In conclusion, the air quality in the Chicago area remains poor, and residents are advised to take necessary precautions to stay safe. The chance of severe storms and high levels of ozone makes it essential to stay informed and up-to-date with the latest weather forecast.
Frequently Asked Questions
Q: What is the current air quality index in Chicago?
A: As of 5:45 a.m., Chicago’s air quality index was ranking in the “good” category, according to AirNow.gov, but it was expected to worsen as the day goes on.
Q: What are the main causes of the air quality alert?
A: The air quality alert is mostly due to high levels of ozone, which occurs when sunlight reacts with pollution, rather than smoke from Canadian wildfires.
Q: What can residents expect in terms of weather for the rest of the week?
A: Showers are possible again on Thursday, with a big temperature drop expected. Lower humidity and temperatures in the 70s and 80s will continue into Friday, but Friday night through the weekend, “periodic bouts of showers and thunderstorms” are expected.
Q: Is there a chance of severe storms?
A: Yes, there is a chance of severe storms, with the strongest storms capable of producing damaging winds as high as 60 miles per hour, and torrential downpours leading to localized flash flooding.
Q: Can a tornado be ruled out?
A: No, a tornado cannot be ruled out, according to the NWS.
