In Jack London's short story, "To Build a Fire," I think the landscape and weather are antagonists.
There are two kinds of conflict: internal and external. External conflict consists of man vs. man; man vs. the supernatural (or God); man vs. society; and, man vs. nature. This last one would most certainly apply to London's short story. This is certainly the deadliest conflict the man in the story faces.
The author has used the weather (especially) to educate his audience as to the importance of building a fire in the cold in the Yukon. The cold is clearly described with the following imagery that details the tobacco juice the man is unable to spit: it freezes and then shatters like glass. This image gives the sense of "damage beyond repair."
...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 result was that a crystal beard of the colour and solidity of amber was increasing its length on his chin. If he fell down it would shatter itself, like glass, into brittle fragments.
The cold is again described in terms of the man's experience with cold in the past, and how easily exposed skin on his body becomes numb. This is also foreshadowing:
Once in a while, the thought reiterated itself that it was very cold and that he had never experienced such cold. As he walked along he rubbed his cheekbones and nose with the back of his mittened hand...But rub as he would, the instant he stopped his cheekbones went numb, and the following instant, the end of his nose went numb.
The landscape becomes an antagonist (a dangerous one) when he turns a sharp corner and happens upon a frozen creek. While the man knows that the creek is solidly frozen, he is also aware that warmer springs linger unseen, which makes the ice in these places fragile and, therefore, deadly. He tries hard to avoid any water.
He reiterates the danger of the cold yet again:
And to get his feet wet in such a temperature meant trouble and danger.
When the man stops to eat, we read again of the threat of the cold, but this time we get the sense that it is not only an enemy, but a quiet and ruthless one. It moves slowly: so slowly, that the man is not sure what is numb and what is not.
He had forgotten to build a fire and thaw out. He chuckled at his foolishness, and as he chuckled he noted the numbness creeping into the exposed fingers. Also, he noted that the stinging which had first come to his toes when he sat down was already passing away. He wondered whether the toes were warm or numb.
The man then makes two mistakes. He gets his feet wet. He knows the severity of the threat:
When it is seventy-five below zero, a man must not fail in his first attempt to build a fire— that is, if his feet are wet. If his feet are dry, and he fails, he can run along the trail for half a mile and restore his circulation. But the circulation of wet and freezing feet cannot be restored by running when it is seventy-five below.
His second error is in building a fire under a tree; he has been pulling twigs from the tree to feed the fire. It makes the branches unstable and the snow falls off of the boughs of the spruce's flat, board-like branches. The fire is smothered.
The man was shocked. It was as though he had just heard his own sentence of death.
The man does, in fact, freeze to death—"killed" by weather and the landscape.