The setting of Jack London's "To Build a Fire" takes place during the late 1890's. That date is never stated in the story, but the reader knows that the man is partaking in the Klondike Goldrush in the Canadian Yukon. Beyond that, there isn't anything specific about the exact location. London's goal with the setting of this story isn't the exact spot. London's goal with the setting is to describe the harsh conditions that the men endured during this gold rush. It's cold. Really cold. So cold that when the man spits his tobacco, it freezes in midair and cracks apart. He's got stuff frozen to his face, too.
"The man's red beard and moustache were likewise frosted, but more solidly, the deposit taking the form of ice and increasing with every warm, moist breath he exhaled. Also, the man was chewing tobacco, and the muzzle of ice held his lips so rigidly that he was unable to clear his chin when he expelled the juice."
The cold setting is also emphasized by man's internal monologue. It's clear that he is an experienced cold weather frontiersman. He knows the danger of the cold. He knows the importance of fire and staying dry. London stresses those points to the reader, so that the reader completely understands what will happen to the man if he fails at keeping warm in the extreme colds of the Yukon. Perhaps all of the man's knowledge makes him overconfident in his abilities, because he doesn't heed the warning of fellow frontiersmen and the beginning of the story. Regardless, the man chooses to leave, and London's setting narration is good enough where my hands hurt from just reading about the cold.