1. Carry plenty of cold weather clothing, even if you don't think you’ll need it: Heavier coats/liners, stocking cap, facemask, gloves (must allow weapon use), chemical handwarmers, etc. Easier if you have a take-home car to keep stuff available but can also keep much of this in your patrol bag.
2. Maintain your patrol vehicle: Keep your patrol vehicle's gas tank full, and ensure windshield wipers and tires are in good condition and that fluids are full. Something as seemingly insignificant as wiper fluid becomes a serious issue if passing vehicles keep splattering salty slush all over you.
3. Maintain a supply: Have food/water, blankets, signaling devices, a shovel, sand, etc. in your patrol vehicle in the event you get stranded somewhere. This will keep you safe until rescuers and/or plows can reach you.
4. Be sensible: Specifically about attempting proactive patrol when road conditions are deteriorating to dangerous levels. It might make more sense to park somewhere or occupy yourself in the office while waiting for a call instead of getting stuck on unplowed roads, wrecking your patrol car or getting hurt simply for the sake of putting miles on the car.
5. Monitor yourself, co-workers and citizens you encounter for signs and symptoms of cold-related injuries and illnesses: Confusion, drowsiness, a rigid posture, clothing removal, an absence of shivering and rapid breathing and heart rate are some signs and symptoms of hypothermia but some appear late. Numbness, tingling and blanching of the skin are early indicators of frostbite. Prevention is much easier than treatment, so don't wait for any of these signs and symptoms to appear before acting.