That's like Antarctica.Well, since we are telling "cold" stories.. The coldest for me was -40F. I had to do some work inside an environmental cold chamber that was set to -40. It was a tad bit chilly in there, even with cold weather gear on.
Wind chill is meaningless at -51ºF. If you've got exposed skin in those temperatures, the only effective insulation for you is a padded cell.-51F, or -73F with the wind chill.