How to dress for cold weather, explained by an arctic researcher
Cold weather layering tips for the polar vortex, explained is a good article on dressing for the seriously cold.

It’s mostly been discussed here before, but it’s well written and seems appropriate for this thread. I’ve been wearing a ball cap under my hood for a few years now. It’s a bit extra for the top of my head and it keeps the hood out of my eyes. The hood she discusses for the seriously cold is in another league.