I saw an ultralight runner doing Whitney 3 days ago. It had been 10 F on the summit that morning. He was in shorts and shirt, no day pack. On the way down from the summit I walked as fast as him, at least net speed. He would run, then stop and tell everyone he met that his (gloveless) hands were cold. someone who knew him said he was an experienced UL from another state. I tried to tactfully point out that there were no 14,000 footers there
