Cold here, cold in Florida -- and beyond

Chicagoans shivering in today's arctic cold can take consolation in the understanding that they are not alone.
Very cold air -- bitterly cold in some regions -- holds all of the nation east of the Rocky Mountains in its frigid grip. That constitutes literally two-thirds of the Lower 48.
Lake-effect snow swirling off Lake Michigan continues to cause problems today for residents of the snow-belt areas of northern Indiana and southwest Lower Michigan (and downwind of the other Great Lakes, as well) -- but they take that in stride.
Residents of the Deep South, however, are far less accustomed to the presence of harshly cold winter temperatures. Freezing conditions are pushing literally into south Florida -- and that's not the end of it. "Northern air," greatly modified but still chilly, is forecast to push across the north half of the Caribbean Sea by Friday.
--By Richard Koeneman, WGN Weather Center Meteorologist