A thick plume of smoke from wildfires in Canada and Minnesota continued to blanket Boston and much of southern New England for a second day on Wednesday, leading to hazy skies and reduced air quality. The smoke is expected to continue to impact the region at least through Thursday. Boston University sent out an alert to the community on Wednesday, reminding individuals with respiratory illnesses and heart and lung disease, as well as older adults and children, to limit outdoor activity and consider using a high-quality filtering mask, such as a KN95 or N95 mask, if outdoor time is unavoidable.