Many when in cold climate will just stick with the initial instinct and what more are taught: Shut your jacket and keep all clothes airtight.
Well, that's not always right.
As my army trainer told us,
the natives of Sapmi have clothes that include a belt over the jacket which is normally kept tight, but if they expect long time physical exercise, they remove the belt to ensure the jacket drops from being short to instead medium-length and allows for air to circulate from bottom to top so that the sweat is allowed out.
If it's not allowed out while excretion is anyway heating your body, it will remain while you generate less heat and then it will cool you way more than "nature intended" long term.
That's why you'll find those "annoying" strings mid/bottom of any kind of serious winter outdoors jackets. Open them UP before doing heavy work.