how do you define "best"?  light weight, warmth, shelter from elements,??

What works during a relatively calm winter night could be life threatening during a raging storm.

I have spent lots of winter nights (around 0 F quite comfy in a bivvy sack, perhaps with a light tarp pitched as a leanto.  The bivvy sack adds 5-10 degrees of warmth to the rig.  A three season tent will work well until (when) you encounter a storm.  With snow and wind, you want one rated for four seasons, with good reviews.

My worst bivvy was on the San Francisco Peaks in late December.  Tried for a snow cave, but the snow was total powder and I had a snow hole instead.  Temps were around  minus 35 F.  No sleeping bag, just an extra sweater.  I did have a small stove, otherwise I might not be here today.  

It wasn't the best, but it was good enough.

Selecting a sheltered location can make a big difference.  Avoid the bottom of creeks and drainages and obviously windy places.  Asmall cave or rock shelter can be quite good.

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