Above all else, the primary thing you need to ride in temperatures that you perceive as "cold" is a willingness to expand your horizons.
This is not to say that someone who hung their bike up in September should just go on a sub-zero all-day epic in the midst of January. It is to say that "acclimating" to the temperature is mostly in your head. Jill and Doug aren't any more resilient than any other human being. They've just got experience, and they know what works for them because they bothered to give it a try. If you are Jill or Doug and are reading this, I'm sorry I gave away your dirty little secret.
Through experience alone, you figure out what works for you in the cold, so it's best to start venturing out for short periods of time or in "somewhat" cold climates, then expand your horizons as the weather gets colder, or start going out longer to determine where your weaknesses are.
Weaknesses can be in clothing:
- too hot
- too cold
- a drafty seam in your favorite winter jersey
- Drivetrain lubrication may be either too thick or doesn't protect from salt
- The ratchet in an old freehub might fail to grab in cold temps
- Your light's batteries might not last as long in the cold