As a record-breaking, sub-zero deep freeze -- or "polar vortex," as it were -- settled in over Chicago and much of the midsection of the United States on Monday morning, ominous-looking steam formed on Lake Michigan where the (relatively) warm water met the frigid air.

While it's more accurate to describe what's happening on the lake as "vapor" rather than "steam" -- due to the temperature -- either way the result is pretty remarkable:



Warm water meets cold air Monday morning in Chicago. (Flickr/bradhoc)



A blanket of fog covers Lake Michigan along the Chicago shoreline Monday. (AP Photo/Teresa Crawford)

Vapor rolls over Lake Michigan.

The scene over Navy Pier.



The Chicago skyline sits as a backdrop as fog drifts across Monroe Harbor. (AP Photo/Charles Rex Arbogast)



Vapor rises from the tops of buildings in the Chicago skyline. (AP Photo/Teresa Crawford)

More vapor along the shore of Chicago.