The Chicago skyline is seen beyond the arctic sea smoke rising off Lake Michigan in Chicago, Il, on Jan. 6. A blast of Arctic air gripped the mid-section of the United States on Monday, bringing the coldest temperatures in two decades, forcing businesses and schools to close and causing widespread airline delays and hazardous driving conditions. Meteorologists said temperatures were dangerously cold and life-threatening in some places, with 0 degrees Fahrenheit (minus 18 Celsius) recorded in Chicago, St. Louis and Indianapolis. The chill was set to bear down on eastern and southern states as the day wore on. (Jim Young/Reutrs)