According to Liam Neeson's account, the temperatures were as low as -40 degrees Celsius (-40 degrees Fahrenheit) in Smithers, British Columbia, where the film was shot. The snow storms/scenes were actual prevailing weather conditions, and not a cinematic illusion produced with CGI (interview: The Tonight Show with Jay Leno: Episode #20.70 (2012)). The cast wore thermals under their costumes for additional protection.
In his glowing review of this film, Roger Ebert stated that in his long career, this was the only time that he actually walked out of his next scheduled screening because it affected him so. "After The Grey (2011) was over, I watched the second film for thirty minutes and then got up and walked out of the theater. It was the first time I've ever walked out of a film because of the previous film. The way I was feeling in my gut, it just wouldn't have been fair to the next film."
This film was denounced by endangered-species protection organizations for its portrayal of wolves as a perpetual threat to humans. It was felt that the film reinforces the ancient cultural notion that humans should follow a kill-or-be-killed policy whenever encountering wolves.
The trivia items below may give away important plot points.
There is a brief scene after the end credits, which shows the alpha wolf lying on his side breathing heavily and Ottway's head resting on the wolf's stomach. If you listen carefully, you can also hear Ottway breathing as well. The scene remains ambiguous as to who is the victor.
The trailer for the movie contained shots of Liam Neeson single-handedly fighting a wolf, which were originally meant to be in the film's climax. However, director Joe Carnahan decided to end the movie just before the fight starts, feeling that the film had reached its emotional height by that time, and a fight involving a computer-generated wolf would feel like an anti-climax. Carnahan later acknowledged that a lot of viewers felt cheated out of the climax that the trailer had promised due to this creative decision.