maybe some thing that dosent have a base form and after it stays in a weather condition it stays that way till a new weather condition occurs:I whole heartedly agree with Sandstorm Castform, but I think an evolution is a bit much. As much as I love Castform (he's in my Top 10 Favorites), I think an evolution would wreck its gimmick. Then again, I thought the same about Porygon 2, and was pleasantly suprised with Porygon-Z, so maybe GameFreak could do something cool for an evolution. As for me though, I have no idea what he'd evolve into.
it started hailing and castform evo becomes hail form. it stays that way untila new conditon happens