Chicago hit a record low of -16 degree Fahrenheit as a polar air mass called a "Polar Vortex" brought the coldest temperatures in about two decades into the city.
Polar VortexIn this satellite handout image provided by National Oceanic and Atmospheric Administration (NOAA), shows the entry of a large area of low pressure, from the Polar Vortex, into the Northern U.S., Jan. 6, 2014.
Polar VortexPassengers heading into downtown wait on an "L" platform for the train to arrive in below zero temperatures, in Chicago, Jan. 7, 2014.
Platforms were crowded and trains were delayed because doors on the trains kept freezing open. Chicago experienced its third consecutive day of below zero temperatures.
Polar VortexWith temperatures at about 22 below zero with a -50 windchill, it was hard to find the beauty in the brutal weather in Bismarck, N.D., Jan. 5, 2014.
Sundogs, a ring of light visible around the sun or moon when light is refracted through ice crystals in the atmosphere, are quite beautiful along Highway 83 north of Bismark.
Polar VortexRyan Metcalf tries to hang on to his golden retriever, Daisy, in Brentwood, Mo., Jan. 5, 2014.
Polar VortexThe Tidal Basin freezes over near the Jefferson Memorial in Washington D.C., Jan. 7, 2014.
Polar VortexU.S. Postal Service letter carrier Jamie Jasmon struggles through snow and below zero temperatures while delivering the mail, in Springfield, Ill., Jan. 6, 2014.
Polar VortexCommuters make a sub-zero trek to offices in the Loop in Chicago, Illinois, Jan. 6, 2014.
Polar VortexMichael Stanton walks between houses covered in ice from sea spray along the shore in Scituate, Mass., Jan. 3, 2014.
Wind-whipped, fluffy snow continued to fall across the state, buffeted by wind gusts at around 40 miles per hour. National Weather Service reported Friday morning that the temperature in Boston was 2 degrees, but 20-below when the wind chill is factored in.