PokéBase - Pokémon Q&A
1 vote

i guess it would rock becuse sandstorm is rock, but it just seems wierd that he doesnt transform...

One possible reason is that weather ball originally became physical when used in sandstorm, which sets sandstorm too far apart from the other three weathers.

3 Answers

1 vote
Best answer

It just doesn't. GameFreak probably didn't want it to be changed. Possible theories:

  • Castform would need to be Rock-looking, and would be a huge contrast from the cuter versions of it in sunny, rainy, and hail weather.
  • Castform would get a SDef boost if it turned Rock type in the sand, making it superior to the other forms, and GameFreak wanted to keep it balanced between the forms.
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It could have been GROUND type :P (sorry for necro-posting)
7 votes

Sandstorms aren't technically a "weather" phenomenon (speaking of the real world). Castform changes form due to the forecast, hence the name of its ability. A sandstorm would technically be a natural disaster, much like thunder or a hurricane, which are other moves in Pokemon which relate to weather. That being said, the weather associated with each of Castform's forms are phenomena that originate in the sky, i.e. sun, rain, and hail, while sandstorms and fog are phenomena that are more local to the terrain. It would make sense then that Castform only changes form for those three types of weather.

Sandstorms are technically weather conditions, like tornadoes and floods, yes they're also natural disasters but they are still considered weather conditions.
3 votes

Castform is based on a water molecule, and the weather the forms are based on the forms of water

Sun is for water vapor

Rain is liquid water

Hail is frozen water

Sorry I flagged for a second I meant to comment "you aren't supposed to answer posts that already have a best answer"
Right, I thought about it.