In the town there are puddles of water, when everything else is frozen.
At numerous times when they are going through the mountains, it is obvious that the horses are walking in plowed trenches.
None of the horses has a winter coat of hair.
At the end, it is supposed to be so cold that the two remaining bad guys die of hypothermia. Judging by the breath of both horses and men, the weather is not really that cold. In fact, numerous times, there is no visible vapor at all.
Tex shoots his horse after it breaks its leg and later shoots Starrett's horse in an attempt to stop him escaping. Both times, the horse can be seen moving on the ground after it is supposed to be dead.
In the mountain scenes, the trees are frequently still and the snow not blowing despite the whistling sounds of a high wind.
The stacks of precisely-cut firewood that are often seen in the village must have been made by using 20th-century machinery.