As I got older, I found my tolerance for cold weather got less... I also suffer from "non-allergenic rhinitis" which means my nose runs like a seive with any heavy breathing much below 50 degrees.

I found that riding my patrol bike in the colder weather just didn't cut it. If you put on enough "gear" to stay warm, you'd die if you had to answer a call and go into a building for more than a few minutes.
Also, bike-patrolling is not that energetic.
However, I went out mountain biking on a sunny 25-degree day once years ago, and was soon shedding clothing! The hard work of riding the trails was plenty to keep warm. (Just as with most energetic Winter sports.)
Any more, I just set up my trainer and spin in front of the TV. Be sure to set up a fan of some sort.