Of course it will differ between people. Not trying to say anything about say people with asthma etc. I've slept in 0F (about -18C) and all I felt was a little

Of course it will differ between people. Not trying to say anything about say people with asthma etc. I've slept in 0F (about -18C) and all I felt was a little "chilly feeling" in the lung area but everything was totally fine. This was outside. Of course you make sure that everything else is warm, including especially the head, where you loose a lot of warmth actually. I bet it wasn't the fact that the air she was breathing that was 'cold' but that she got cold overall.