To Build a Fire remains one of Jack London's most famous and influential stories, being a simple tale of man vs. nature in a harsh environment. By describing the facts without embellishment and allowing no false drama, London shows a place where man is not meant to live.
The nameless protagonist and his husky dog travel by foot towards a campsite where other men are mining gold. In his haste, he stumbles into a frozen spring, gets wet, and cannot make a fire because his hands have become numb from the cold. The Yukon is no place for men, or even for dogs, although the dog is better suited and probably survives the end. Throughout the story, London describes the hostile, frozen world, and even before the man's slide into ruin begins every mention of snow and cold seems oppressive:
As he turned to go on, he spat speculatively. There was a sharp, explosive crackle that startled him. He spat again. And again, in the air, before it could fall to the snow, the spittle crackled. He knew that at fifty below spittle crackled on the snow, but this spittle had crackled in the air. Undoubtedly it was colder than fifty below—how much colder he did not know.
(London, eNotes eText)
Every exposure to the air leeches some of the heat from his body; forget the snow and lurking water, even the air is too cold to survive in! Fire, then, is the only civilizing thing in this world, and after he becomes wet, the man is prevented from lighting a fire to warm him through the night by the air, which freezes his fingers, causing him to drop matches and fumble the tinder; by the snow, which falls on his fire and puts it out; and by the tinder itself, as he shivers a too-large piece into the flame.
London's sparse, simple prose gives the Yukon a close, unforgiving feel, even as it is a wide and open landscape; truly, the cold is oppressive, and it makes the man shrink into himself until he is as cold as the land and air around him.