Millions of Americans brace for severe weather as wildfire smoke smothers the Midwest

Parts of the Southeast could see wind gusts reach 70 mph, putting millions of Americans under severe weather threat. Meanwhile cleanup is underway in the Northeast after powerful storms pummeled the region, with tornadoes touching down in Pennsylvania. And Canadian wildfire smoke continues to blanket parts of the Midwest with Minneapolis, Detroit and Chicago ranking amongst the worst air quality in the world. NBC News' Valerie Castro reports.