Yep, the sun's finally going down. If you couldn't tell by the low angle to the horizon, the temperature will tell the tale.
It is now -74F. But, the all-important windchill is something you won't find in Minnesota or North Dakota: -112F. Our air density is also dropping which makes our 9300ft altitude seem like 11, 276ft to our lungs.
To be honest, I don't feel much difference. Cold is cold; high is high.
Carry on soldier.