The Lincoln Park Zoo's polar bear, Anana, is being kept in a climate-controlled area through 'Chiberia.' View Full Caption Lincoln Park Zoo

CHICAGO — You know it's too cold when the city's polar bear is kept indoors.

Anana, the Lincoln Park Zoo's lone polar bear, is keeping warm in a "climate-controlled" area in the wake of the city's below-zero temperatures, according to zoo spokeswoman Sharon Dewar.

"She doesn’t typically enjoy the very cold much," Dewar said of the 12-year-old polar bear. "Few of us are accustomed to this cold."

Polar bears in the arctic would typically put on a fat blubber layer going into late winter, Dewar said, but Anana, a city bear, doesn't have that blubber layer this year due to our warmer climate.

In the wild, a blubber layer up to five inches — plus their black skin under their white fur — helps keep them warm. Small ears and a short tail also help them adapt to cold weather, the zoo says.

Its Too Cold For the Polar Bear in Chicago View Full Caption Lincoln Park Zoo

But living in the city of Chicago, "typically they wouldn’t need that insulation and it would make them uncomfortable going into summer," Dewar said.

Dewar said Anana, a naturally solitary animal, will be spending her time alone for the nearly -40 degree wind chills expected to hit Chicago Monday — but the polar bear will be warm.