In dry weather or snow, keeping hands warm isn't too big of a problem. One can essentially just use downhill ski gloves or similar. That's what I used when I rode my beamer cross country in mid-December 45 years ago. Since one is creating a lot more warmth and blood circulation biking than sitting on a moto or chairlift, they don't even have to be all that special, just insulated and windproof.

In the PNW, we have a slightly different, more difficult problem. How to keep hands functional when on a long ride at 36° in a steady rain. Best thing I've found are Xenon Gore-Tex gloves. Haven't tried them at 20° because I don't ride on ice. I should try them skiing, just to see.