But the temperature did not matter. He was bound for the old claim on the left fork of Henderson Creek, where the boys were already.
The man does not think of anything but getting home to "the boys" and eating supper. His mindset is simple, void of any complex thinking, which means he does not see the danger of a temperature so low, that spittle freezes the minute it hits the air.
Chilcoot Pass
A mountain range on the coastal borders of Alaska and British Columbia.
There was no sun nor hint of sun, though there was not a cloud in the sky. 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. This fact did not worry the man. He was used to the lack of sun. It had been days since he had seen the sun,
The repetition here regarding the lack of sun is meant to emphasize the gloomy, almost hostile environment of the freezing Yukon. Despite it being a clear day, there is no light to clear away the pervading gloom that surrounds the man.
Fifty degrees below zero was to him just precisely fifty degrees below zero. That there should be anything more to it than that was a thought that never entered his head.
The man believes he is experienced enough and knows enough about the Yukon not to fear the dropping temperatures. This quote foreshadows his underestimation of the cold and ultimate demise.
he knew that a few more days must pass before that cheerful orb, due south, would just peep above the sky-line and dip immediately from view.
Refers to June solstice in the Yukon, during which the sun rises just above the horizon for 24 hours before setting again.