The story takes place in the winter, and the cold weather is seen often in the dialogue and narration. The first scene, which sets the tone for Tub's mistreatment by Kenny, focuses on how he waits in the snow because Kenny didn't arrive on time, and from then on, the cold snow is a major symbol:
The snow was shaded and had a glaze on it. It held up Kenny and Frank but Tub kept falling through. As he kicked forward, the edge of the crust bruised his shins.
(Wolff, "Hunters in the Snow," classicshorts.com)
Later, when Tub and Frank are trying to get Kenny to the hospital, they keep stopping. They make excuses, but the real reason they keep stopping is because of the cold; the truck window is broken and they can't stay warm. Their small bonding over personal issues while Kenny slowly loses blood is accelerated by the cold, and in the end they take his blankets for themselves and continue driving, not caring if Kenny freezes.