Temperatures Set to Plunge 20 Degrees as 'Polar Vortex' ReturnsThe chilly air that invaded in the plains is now making a march across the country with cities everywhere from Minneapolis to Dallas.Get more newsLiveonPrintSaveCreate your free profile or log in to save this articleDec. 8, 2016, 7:34 AM UTC / Updated Dec. 8, 2016, 7:34 AM UTC