Well, I have a policy that I don’t try to explain individual moves or abilities on specific Pokémon unless they seem to be important parts of the Pokémon’s design, on the grounds that it’s just asking for trouble. I think Cloud Nine is one of those powers that we just have to chalk up to “magic.”
But what kind of magic?
It’s interesting that it’s so exclusive – prior to the introduction of the Dream World, Cloud Nine was the signature ability of Psyduck and Golduck; the only other Pokémon who could block weather effects was Rayquaza, through his Air Lock power. Cloud Nine appears to create an area of calm, neutral weather around the Pokémon using it; it makes a sort of intuitive sense that Altaria would have a power like this because 1) she’s a cloud Pokémon, and 2) a lot of her other characteristics and powers are related to calmness and serenity. Golduck’s other ability is Damp, another ability related to enforcing calmness and shutting down chaotic powers, and Cloud Nine could explain Golduck’s famous strength as a swimmer (Sapphire version claims that even the stormiest of seas do not hinder him). As for Lickilicky… I’m afraid I’m honestly not sure. Lickitung and Lickilicky don’t have any other notable powers related to either calmness or weather. I’ve always thought they were silly Pokémon anyway, so I’m not hugely bothered by that, but it does bug me, because normally when Game Freak give a rare move or ability to a Pokémon they have a clear reason in mind… I just can’t figure out what it is.
Pokémaniacal 