The Illinois Environmental Protection Agency extended an air quality alert into Monday for northern and central Illinois as a second wave of wildfire smoke settled over the area.
The smoke was expected to clear by Monday evening, according to AirNow, a website that combines data from county, state and federal air quality agencies nationwide. On Saturday night, smoke containing high levels of particulate matter returned to Illinois.
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Gino Izzi, senior meteorologist at the National Weather Service, said he expected it to “kind of fester” in Illinois most of Sunday before likely blowing back across Lake Michigan on Monday.
Conditions for the beginning of the workweek were forecast at a minimum to be unhealthy for sensitive groups, which include people with heart or lung disease, older adults, teens and children. These groups should avoid long or intense outdoor activities.
On Sunday night, Chicago had the worst air of any major city in the United States and the fifth-worst air in the world, according to Swiss air quality company IQAir.
Weather service meteorologist Ricky Castro said there was a potential Monday for severe weather in the Chicago area.
Rain can increase visibility when there’s smog, but its effect on air pollution is less certain, the weather service said.
On Thursday, wildfire smoke from Canada and Minnesota caused PM2.5 levels in parts of northern Illinois to quadruple the previous record set in Cook County during 2023’s fires. Fine particles known as PM2.5 can be emitted by factories, power plants, diesel and gasoline vehicles, residential fireplaces and wildfires. PM2.5 can harm human health and sometimes be deadly. Initially, fine particulate matter may cause a burning sensation in the eyes and nose. But because of its small size, it can settle deep in the lungs and cross into the bloodstream.
As climate change intensifies, concerns grow about air quality events that disrupt daily life becoming the norm. Scientists say climate change from human activities is making conditions like drought more common, thus increasing the size, frequency and severity of wildfires. Wind patterns also add a layer of unpredictability to the reach of bad air from intensifying, longer-lasting wildfires.
The smoke that traveled out of Illinois and into Michigan and Wisconsin on Friday was pushed back into the region Saturday night by a cold front, Izzi said.