Cold weather game.
It isn't just a matter of discomfort, it is a matter of fundamentals that you learn over a long period of time, not just a one day adjustment.
The way you hold the ball, the way you throw the ball, the way you catch the ball, the risks that you cannot take in the cold, etc etc.
Limits the passing game.
Emphasizes the running game.
Etc etc.
It is a huge factor when it is THIS cold.
This favors Pittsburg significantly.