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Snow plows clear downtown lanes on Interstate 75/85 during a winter storm on Wednesday, Feb. 12, 2014, in Atlanta.  Across the South, winter-weary residents woke up Wednesday to a region encased in ice, snow and freezing rain, with forecasters warning that the worst of the potentially "catastrophic" storm is yet to come.

David Tulis/AP

A snow plow clears downtown lanes on Interstate 75/85 during a winter storm on Wednesday in Atlanta.

Team USA huddles around the net before the game against Switzerland during the 2014 Winter Olympics women's ice hockey game at Shayba Arena, Monday, Feb. 10, 2014, in Sochi, Russia. (AP Photo/Matt Slocum )

Matt Slocum/AP

Team USA huddles around the net before the game against Switzerland during the 2014 Winter Olympics women’s ice hockey game at Shayba Arena, Sochi, Russia 

US President Barack Obama attends the National Prayer Breakfast in Washington, DC, on February 6, 2014.

Jewel Samad/AFP

US President Barack Obama endorses the National Day of Prayer by attending the celebratory breakfast in Washington, DC, on Thursday

A man walks past a sculpture covered by a light dusting of snow in Baltimore.

Patrick Semansky/AP

A man walks past a sculpture covered by a light dusting of snow in the US city of Baltimore

Members of Code Pink protest group march against U.S. President Obama and NSA before arrival at Department of Justice in Washington...The founder of the protest group Code Pink Medea Benjamin (L) and Daria Lindsey (R) wears large sunglasses as they  protest against U.S. President Barack Obama and the NSA before his arrival at the Department of Justice in Washington, January 17, 2014. Obama banned U.S. eavesdropping on the leaders of close friends and allies on Friday and began reining in the vast collection of Americans' phone data in a series of reforms triggered by Edward Snowden's revelations.  REUTERS/Larry Downing

Larry Downing/Reuters

Medea Benjamin, left, and Daria Lindsey, right, of the group Code Pink protest against US President Barack Obama and the NSA before his arrival at the Department of Justice in Washington. Mr Obama banned US eavesdropping on the leaders of close friends and allies on Friday and began reining in the vast collection of Americans’ phone data in a series of reforms triggered by Edward Snowden’s revelations. 

A man walks past a car partially covered in ice in Baltimore where temperatures continue to remain well below freezing.

Patrick Semansky/AP

North America has been hit by the coldest temperatures in decades after a a polar vortex led to extreme weather conditions. In Baltimore, temperatures remain well below freezing, with ice forming on buildings, cars and roads.

Visitors walk through the holiday lights display "ZooLights" at the Lincoln Park Zoo in Chicago, Illinois...Visitors walk through the holiday lights display "ZooLights" at the Lincoln Park Zoo in Chicago, Illinois

Jim Young/Reuters

Visitors walk through the holiday lights display “ZooLights” at the Lincoln Park Zoo in Chicago, Illinois.

Protesters chained together block the entrance of an immigrant detention center on December 10, 2013 in Elizabeth, New Jersey. A coalition of immigrant advocacy groups marked international Human Rights Day, staging the civil disobedience action at the Elizabeth Detention Center, and eight protesters were arrested by police. Organizers said the event was designed to draw attention to the continued mass deportations of undocumented immigrants by U.S. Immigration and Customs Enforcement (ICE), as well as Congress' inability to pass immigration reform. The Obama administration is on track to have removed 2 million immigrants from the United States, the most of any presidential administration.

John Moore/Getty Images

Protesters chained together block the entrance of an immigrant detention centre on Tuesday in Elizabeth, New Jersey. A coalition of immigrant advocacy groups marked international Human Rights Day by staging the civil disobedience action at the Elizabeth Detention Center where eight protesters were arrested by police. Organisers said the event was designed to draw attention to the continued mass deportations of undocumented immigrants by the US Immigration and Customs Enforcement, as well as Congress’s inability to pass immigration reform.

A commuter waits on a train during a winter snowstorm Tuesday, Dec. 10, 2013, in Philadelphia. Accumulations of 3 to 6 inches were expected as the National Weather Service issued a winter storm warning for the Eastern Seaboard, including Baltimore, Washington, D.C., Philadelphia and Wilmington

Matt Rourke/AP

A commuter waits for a train during a snowstorm in Philadelphia, US

A shopper rests in the shoe section of the Macy's Herald Square store, in New York. Instead of waiting for Black Friday, which is typically the year's biggest shopping day, more than a dozen major retailers opened on Thanksgiving this year.

John Minchillo/AP

A shopper rests in the shoe section of Macy’s Herald Square store in New York on Black Friday, the US’s busiest shopping day of the year