Like most other short haired breeds, Pitbulls are not the most winter friendly of animals. As the weather closes down, they are going to need some help one way or the other. A heated doghouse or a nice spot by the fire may be in order, especially when it is both wet and windy outside.
Another alternative might be to play a little bit of dress up with your pooch and get them into a nice warm sweater that serves as a substitute for the Saint Bernard coat they were not born with. Dog sweaters for Pitbulls offer some additional benefits over and above keeping them warm.
It also humanizes them. Due to their menacing reputation, many non-Pitbull owners do not understand how loyal, loving, and intelligent the breed is. Getting them into a whimsical sweater is one way of helping people to see that they are just dogs like all the others.