In several scenes, the cinematographer quite noticeably uses filters that create and orange and dark blue gradients at the top of the frame to simulate morning and evening skies. When the camera follows the action the gradient (which has a noticeable curve in the center) doesn't move while everything else does. When P.I. and his companions are at their campfire, P.I. stands up and the filter turns his face dark blue.
In one scene a character states that they've seen colder weather. This scene takes place at a latitude that sometimes sees temperatures drop to 17°. The coldest temperature recorded in Texas was -20° fahrenheit, without factoring in wind chill.