The climax of Jack London's short story To Build a Fire occurs when the story's protagonist, simply referred to as "the man," warming himself after falling through the ice in the extreme, frigid cold of the Yukon Territory, discovers the folly of building a fire beneath a snow-covered tree. As anybody who has experience camping or hiking in the woods during winter knows, building a fire underneath a snow-covered tree will invariably result in the snow-covered branches buckling under the weight of that snow and dumping the icy powder onto the meticulously-crafted fire, extinguishing the individual's sole source of warmth. The point of London's story, however, is precisely this: the folly of man's insistence on believing that he can conquer nature, and the dangers of arrogance.
London's protagonist is presented as a newcomer to the harsh, forbidding coldness of the far-north during the middle of winter. He is also depicted as suffering from an acute sense of intellectual superiority, cavalierly casting aside warnings of dread, firm in the belief that he knows better. Observe, for instance, the following passage from early in To Build a Fire:
"He was a newcomer in the land, and this was his first winter.
"The trouble with him was that he was not able to imagine. He was quick and ready in the things of life, but only in the things, and not in their meanings. Fifty degrees below zero meant 80 degrees of frost. Such facts told him that it was cold and uncomfortable, and that was all. It did not lead him to consider his weaknesses as a creature affected by temperature."
As the man continues his trek through the woods for his meeting with "the boys," he repeatedly demonstrates disdain for the warnings of "the old man on Sulphur Creek." The latter's warnings against attempting to undertake a hike under such conditions as existed are ignored, and the result, or resolution of London's story, is the man's death. And, it is only when he knows that he has failed in his mission, and that his death is near, that he finally acknowledges that the warnings he had ignored were prescient. As London brings his story to an end, his protagonist murmurs to himself regarding the old man from Sulphur Creek's advice, “You were right, old fellow. You were right."
That London titled his story "To Build a Fire" is a clear indication that he intended the climactic scene to be that which involved the construction of a fire under preposterous conditions (i.e., under snow-covered branches). That his protagonist should perish from the harsh winter conditions due to his arrogance and ignorance is an apt resolution of the central conflict of man versus nature.