In theory, we can and usually do. The UPS man wears shorts all year long. We only rarely cover our faces no matter how cold, although where I live, it doesn't get below zero Fahrenheit very often at all and to our relatives in Minnesota, that isn't even cold.
I think it's an important topic, somewhat more so if one is interested in being nude. But conditions vary widely, even wildly, so generalizations will have a lot of exceptions. In heat and cold both, our own experiences seem to defy everything we've always heard. We don't die that easily, evidently.
Although I have frequently been outside and nude when temperatures were well below 50 degrees F., I haven't been out for very long like that. But I've hiked all day nude in temperatures of around 90 and didn't seem to suffer for it. In fact, I never seem to drink as much water as 'they' say you should. Even more surprising, I don't even remember sweating as much as I normally do. It may be that my memory is bad, though. But as I said, conditions vary. I was hiking in the hills (either up or down the whole way) and in the shade nearly the whole time, which may be the key factor. Also, the weather was very humid, which is typical. Part of the way was along a ridge with a light breeze that may have made a difference. I never got thirsty, either, but I did drink some water. This was all with wearing a small pack.
In contrast, here at home I usually take a walk about every day or two, wearing clothes and carrying the same pack. The walk takes me through the woods, with some gentle climbing, and a little time in the sun. Half of the distance is on a muddy trail and usually includes wading a creek once or twice, depending on which trail I take. When I get home, most of my clothes are soaked with sweat (and I'm a little muddy, too). For more than one reason I can't be nude and even shorts are a bad idea because of where I walk. Interesting difference, although I don't get particularly thirsty. But the sweat just drips from my face, which bothers me more than anything.
