Officials said air quality warnings remained in effect across parts of the United States on Saturday as smoke from wildfires in Ontario and Minnesota continued to drift south. Tens of millions of people in Canada and the United States have been breathing unhealthy air for several days, prompting business closures, event cancellations and evacuations in several communities. The poor air quality was expected to persist in the mid‑Atlantic and northeastern regions through Saturday afternoon, with a chance of thunderstorms that could provide brief relief but also bring flash flooding and high winds. In the Midwest and Great Lakes region, including parts of Illinois, Michigan, and the vicinity of Detroit and Washington, D.C., air quality ranked among the worst globally, according to IQAir. Health officials urged people with heart or lung conditions, older adults, pregnant individuals and children to limit outdoor activity, and free K95 masks were distributed in New York, New Jersey, Pennsylvania and other northeastern states. Bob Oravec, a lead forecaster at the National Weather Service, said the smoke is likely to remain widespread because the fires are burning largely unchecked. While some temporary improvement may occur with weekend storms, the wildfire situation is expected to continue for the foreseeable future.