In tonight's episode of Frozen Planet, it's pretty cold - even more than usual - as winter arrives in the poles and temperatures plummet to -70C.
Sir David Attenborough guides us through complete darkness at the polar extremes, as winds reach 120mph. As if things aren't tough enough already for our Arctic inhabitants, they now have these dastardly weather conditions to compete with.
A female polar bear treks to the mountains to give birth, while the entire world's population of spectacled eider ducks braves the weather in a giant ice hole.
And we'll see another amazing hunt, in a raw battle for survival, as a pair of wolves take on bison in the deep snows of northern Canada.
Finally, giving us just enough cuteness so that this real showcase of life and death doesn't bring its loyal viewers down, tonight's Frozen Planet also shows new-born polar bear cubs hiding out in a snowy den where their mother gave birth to them. The shots of the tiny, blind, white cubs (see photos below) mewing for milk will warm your heart, even if it is cold outside.
SLIDESHOW: See photos from Frozen Planet episode 5...
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