The previously mentioned road conditions will obviously be quite a wrench in the works, but even on-foot transit will be affected; certain routes will be made difficult to locate or follow, or simply impossible.
Obtaining water from natural sources will be far more challenging and laborious; it is hard to drink water that is frozen! You’ll need to thaw it first.
Even your daily readiness procedures will be impacted. Just ask anyone who carries a pistol for self-defense how challenging it gets keeping the gun accessible under bulky, heavy layers of suitable winter clothing.