Unhealthy levels of wildfire smoke expected to 'kind of fester' most of the day, weather service says

Finnegan Belleau, Chicago Tribune on Jul 19, 2026

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Smoke from Canadian wildfires returned to Illinois on Saturday night as air quality remained at “unhealthy” levels, according to AirNow, a website that combines data from county, state and federal air quality agencies nationwide.

Gino Izzi, senior meteorologist at the National Weather Service, said he expected the smoke to “kind of fester” in Illinois most of Sunday before likely blowing back across Lake Michigan on Monday.

On Thursday, wildfire smoke 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.

The smoke traveled out of Illinois into Michigan and Wisconsin on Friday, Izzi said. However, a cold front pushed it back into Illinois on Saturday night.

The Illinois Environmental Protection Agency issued an air pollution alert Sunday for all of Illinois, except for the St. Louis Metro East region. According to a news release, the smoke was anticipated as “at or above unhealthy for sensitive groups.” These groups include people with heart or lung disease, older adults, teens and children.

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.

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