What is the setting of "To Build a Fire" by Jack London?

When the story opens, it is morning and the man and his dog are in the Yukon. The Yukon is the northwestern part of Canada and lies east of Alaska. London describes the sky as "cold and grey, exceedingly cold and grey." The man thinks it must be fifty degrees below zero. "Undoubtedly it was colder than fifty below—how much colder he did not know." 

There are no clouds, but there is no sun. The landscape is cold and covered in snow and ice. The sky is gloomy. "It was a clear day, and yet there seemed an intangible pall over the face of things, a subtle gloom that made the day dark, and that was due to the absence of sun." From the north to the south, all he can see is snow. There is only one strip of spruce trees that breaks up the ubiquitous ice and snow. London makes it a point to describe how cold and unforgiving the landscape and weather are. He also stresses how the foolish man is initially not concerned about this. He is new to this area. This is what will lead to his downfall. He does not understand how dangerously cold it really is.

This is a good example of Naturalism in literature. Whereas some Naturalist works focus on social forces, stories like "To Build a Fire" highlight the power and reality of nature.