20+ yrs of living in northern MN has taught me much about dressing for the cold. I wear military surplus 'bunny boots' good for -60 temps, I've stood on the ice fishing @ -25F for 3-4 hours at a time wearing these boots. If your feet remain dry & warm then that's more than 1/2 the battle of retaining warmth. Above the feet up I just dress for the occasion, DuoFold longjohns rule for warmth and comfort imo and spending any time outside requires good gloves and head gear for sure, I like a MadBomber style surplus cap I wear over my wool navy watch cap.
Military surplus is the best cold weather gear imo & functional like a mofo as there's always extra pockets and features built in. Our military is forced to over produce these items because to find ourselves w/o them is inexcusable. Surplus clothing is available year round online through many sources. yeah I can afford nice comfy rain suits for fishing but you gotta know you'll find me dry and warm under the surplus poncho I've had for about 40+(yup, mid 60s) years now. Cheap to own but built to last, it's military grade tough.......
+1 on surplus or used military gear for cold weather gear. I still use my flame resistent long underwear that I was issued with my other flight gear in the early 80's. more than 25 years ago and my long underwear still work!. They hang off me like a mo fo but they are still warm. I had alot of other items that I had to turn back in or pay for so I did not keep the parka, too expensive for me to purchase.
However I fucking absolutely kept my flight jacket, its my pride and joy. That and my custom fitted flight helmet which they neglected to ask me to return so I kept it. It now adorns one of my bookshelves in my home office.
Many memories flying, military aircraft can be cold as fuck all. Your gear has to keep you warm or you are fucked for the mission.