Googled this, but most of the results pointed to chronic conditions, which I don't think is the case here. I was up in the Hoover Wilderness last week, and my second night out found myself shivering uncontrollably in my sleeping bag, but I didn't feel cold. According to reports I read later, it was 36F. Any ideas what might have been going on? Dehydration may have been in play; I lost five pounds over the two days, and gained it back on my second day home . Nutrition as well, since 1, I forgot to pack some of my intended food, and 2, I felt mildly nauseated when I tried to eat anything. Altitude maybe? Although it was barely 9000'.