In the troposphere, which has the bulk of the atmospheric mass, it's colder at higher altitudes due to adiabatic lapse. Gas giants have several different chemicals that condense into cloud decks at various altitudes. On Jupiter, for example, water clouds occur about 100 km below ammonia clouds.
Suppose a gas giant got so cold that Hydrogen and finally Helium began to condense in the upper atmosphere. This does not happen in our solar system because there is too much sunlight and internal heating, but it would likely be the fate of an orphan planet left to cool for a long enough time. Unlike the case with water or methane, the entire upper atmosphere tries to condense into cloud droplets. How would such an atmosphere behave?