Tens of millions of residents along the East Coast are bracing for several inches of snow Sunday followed by dangerously cold temperatures that will take hold in much of the country from the Northern Plains to the tip of Maine.

The updated forecast on timing and track of the storm calls for the snow to end from southwest to northeast as midnight approaches. “The heaviest precipitation looks to occur between roughly 4 and 9 p.m. during which time snowfall rates could reach or exceed 1 inch per hour,” the National Weather Service said.

A polar vortex is slated to sweep most of the continental US bringing winter storm warnings and a hazardous freeze to millions.