Not at all, actually! You see, Alola has a very similar climate to Hoenn, one of the banette species’ native ranges, so if anything, your banette may be right at home in Alola.
However, it’s important to note that like many other ghost-type pokémon, banette is nocturnal and may not fare so well in bright sunlight. Be sure to give yours plenty of shade to rest in or keep him in his poké ball until sundown.
Happy vacation, @fawcettforever!