I don't know about you but working out in the cold can sometimes be uncomfortable because it makes my muscles extra tight. What helps me is to warm up inside before heading out into the chilly weather.
Before a run or bike ride, I do about 5-10 minutes of light cardio inside. Jogging in place, jumping rope, or going up and down my stairs is just enough activity to loosen up my body and get my blood pumping. When I get outside, it's less of a shock to my system. If you'd rather do your warm-up exercises outside, a hot shower is another great way to loosen up your muscles before a cold weather workout.