The soldiers who fought in The Bulge endured those conditions for months, without "down jackets" or anything like them. Some of them didn't even have boots.
I hope I'm never that cold again, this side of the grave.
Played golf in the late 60s on a 105° day with a fellow who conspicuously ignored our loud complaints about the heat. When I asked him why, he said, I fought in the Battle of the Bulge. I was so cold that I swore I would never again complain about the heat.