On Earth (or another planet with an identical atmosphere), how high above sea level would a mountain have to rise so that its summit would no longer have any snow on it, not even temporary?
The highest "typical" clouds on Earth are the cirrus clouds around 40,000 ft altitude, but the tops of Cumulonimbus clouds can get higher than 55,000 ft above the equator. But even above 60,000 ft there still occur clouds called polar stratospheric clouds and then there are noctilucent clouds which can be as high as 53 miles - in outer space! Since these are made of ice crystals, could even those deposit on a mountain that is say 60,000 ft in elevation? So actually I don't ask on snow only, but on frost and ice as well. How high would a mountain have to be so that its summit would be bare rock (regardless of whether such mountain is physically possible to persist in the first place)?