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When I was outside a few months back and it was -5 or whatever I went even more overkill, double base layers top and bottom plus a gilet over what I was wearing yesterday, it does seem to help as I've been much worse off in the past as far as cold feet go when it wasn't as cold. Flask of tea and a rechargeable hand warmer running in my pocket was helpful to bring hands back to just cold every time they dipped to bloody cold.
My thinking was that if you're core is super warm it will want to dump that heat, via your hands.