As of Aug. 6, there are about 750 active Canadian wildfires, with at least 190 labeled “out of control,” according to the Canadian Interagency Forest Fire Centre. More than 16 million acres (6.8 million hectares) of land have been scorched this year, making this one of Canada’s worst wildfire seasons on record.

As Canada grapples with one of its worst wildfire seasons on record, smoke from the blazes have prompted air quality alerts across the U.S.

Hundreds of wildfires still burning in Canada are expected to undermine air quality across the Upper Midwest and Northeast into Tuesday.