This week, much of the eastern US will experience some of its coldest temperatures in years. A major winter storm is bringing snow, with up to half a foot expected in parts of the mid-Atlantic and New England, including cities like New York and Boston. Over 70 million people will be under winter storm warnings. As the storm passes, frigid temperatures will follow, with wind chills as low as -40°F in the Northern Plains and sub-zero conditions spreading south to Oklahoma and Tennessee. The cold snap, caused by a disruption in the polar vortex, will lead to dangerously cold conditions in cities like Washington, DC, where inauguration ceremonies were moved indoors. A wintry mix of snow and ice will also impact the South, from Texas to northern Florida.