CHICAGO – Chicago had the worst air quality overnight Wednesday into Thursday, the latest American city to feel the impact of wildfire smoke drifting south from Canada, as states across the Upper Midwest, Great Lakes and Northeast are covered in air quality alerts.

The smoke is being pulled down by the backside of a trough from more than 100 deadly wildfires that are burning in Canada, many of them not under control.

Chicago's health department warned groups that are sensitive to poor air quality to reduce their time outdoors Thursday.

Changes in the weather pattern will see some of the smoke move out of both the Midwest and Northeast by the end of Thursday.

Chicago had an air quality index (AQI) rating of 161 on Wednesday, according to the FOX Forecast Center.

AQI ratings between 200

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