In warmer months, it’s not such a hard argument for the return of the hat. They’re jaunty, cute, even charming — and can protect from the sun.

But January (or February or March) is not a warm month. In fact, it’s pretty darn cold. Yet, look around. You’ll see a goodly number of people outdoors wearing no head protection whatsoever.

For some of us, it’s simply fear of the dreaded hat hair. For others, it’s carelessness: We’ve lost or forgotten our headgear. Whatever your reason for going hatless up to now, the luxurious objects are an excellent reason to reconsider.

New York designer Marc Jacobs’ "trapper hat" ($650) bears little resemblance to the furry ad hoc headgear of the trappers who helped settle the American West, but it is one example of a style that will keep your head warm.

And when it’s brutally cold, those side flaps come down, encasing the ears, too, in extravagant warmth.

Designer Jacobs leaves it for others to argue — and argue they do — about exactly how much body heat escapes through the uncovered head. Estimates range from 7 to 75 percent.

For some scientific to-and-fro on this topic, the Wilderness Medicine Newsletter offers a lively discussion involving hypothermia, cerebral blood flow, muscle oxygen needs and such.

Scalp vasodilatation aside, everyone agrees that it’s common sense to wear a hat when it’s really cold out.