An air quality alert is in effect for all of Massachusetts today due to smoke from Canadian wildfires, and it could be the worst air quality day the Boston area has seen all year. The Massachusetts Department of Environmental Protection issued an alert for "fine particulates" in the air until midnight.

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

People may experience difficulty breathing and throat irritation as Canadian wildfire smoke causes air quality to deteriorate in the Midwest and Northeast.