Temperatures plummeted as a whirlpool of frigid, dense air known as a "polar vortex" descended on much of the United States.
Pilot Hank Cain captured this image of a frozen Chicago while deadheading from Washington D.C. to the Windy City. Deadheading is the practice of ferrying airline crews to their next assignment.
Chicago felt like 31 below this morning as Arctic air from a "polar vortex" locked nearly the entire United States under subfreezing temperatures Tuesday.
Follow Cain on Instagram at @flyhankcain.