Weird light, cold nights

All the weekend thru, we had temperatures of about 3° F/-16° C at night. During the day, they did not rise much, so we had about 19° F. This is unusual. I remember warm Xmas eves in the seventies, 63° F on Dec 24th, 1978.
Last night, it wasn't quite so cold, just 28, but the sky was so bright. Looks weird, doesn't it? This picture was taken at 4:38 in the morning, long before dawn. We don't have more than 3" snow, but a Siberian feeling.
J hates it, I can cope with it. Baltic blood? In my parents' old home, most of the winter temps stayed on the above level, and schools stayed closed when it was below -- 22° F/--30° C.
I'm convinced that a warm cap is the clue. In Germany, most people take pride in going out without a cap. I don't know the offspring of this peculiar custom. I brainwashed my husband into wearing a cap. His rate of sinusitis has decreased from 3 times a year on less than once since then.
Solstice! From tomorrow, the light is coming back and days start getting longer!