(Undated) — Dangerously cold weather is on the way and you can blame the polar vortex. The National Weather Service says much of the U.S. will be shivering in subfreezing temperatures this weekend. The worst of it will be in the Upper Midwest and Northern Plains with wind chill temperatures diving as low as 40 below zero in parts of the Dakotas. And the wicked cold will stick around. Forecasters say the coldest storm of the season will move in this weekend and might stay all through next week.