This is me on 3220m above sea level on Mt. Fuji and totally shattered. The top is at around 3800m above sea level so i "only" had 580m more to climb before i reached the top. At sea level it was ~32C and on the top it was ~2C and freezing. I can tell you that if you go from sea level to 3800m within a few hours you will be impacted by the thin air.