Arctic

An aerial view at night of the downtown Chicago skyline. An Arctic air mass is expected to chill much of the Central Plains and the East Coast through Monday with wind-chill temperatures dropping into the single digits overnight in some places.

Kiichiro Sato/AP

A nightime aerial view of downtown in the US city of Chicago

Greenpeace activist Perrett from Britain attends a bail hearing at a regional court in Murmansk...Greenpeace activist Anthony Perrett from Britain attends a bail hearing at a regional court in Murmansk October 16, 2013.

Dmitri Sharomov/Greenpeace/Reuters

Greenpeace activist Anthony Perrett from Britain attends a bail hearing at a regional court on Wednesday in Murmansk, Russia.

A sign warns residents of the arctic Svalbard islands in Norway of the danger from roaming polar bears, May 26, 2013. Svalbard in Norway's high Arctic, is home to 2,500 people and about 3,000 polar bears. Picture taken May 26, 2013. To match NORWAY-ARCTIC/NYAALESUND.

Balazs Koranyi/Reuters

A sign warns residents of the arctic Svalbard islands in Norway of the danger from roaming polar bears. Svalbard is Norway’s high Arctic, is home to 2,500 people and about 3,000 polar bears. Read more