Ability · Gen 3 · 1 Pokémon
Forecast
Castform's type changes to the current weather condition's type, except Sandstorm.
If this Pokemon is a Castform, its type changes to the current weather condition's type, except Sandstorm. This effect is prevented if this Pokemon is holding a Utility Umbrella and the weather is Rain or Sun.
Forecast was introduced in Generation 3. 1 Pokémon and forms can have it.
Pokémon with Forecast
As a regular ability (1)
CastformForecast FAQ
What does Forecast do?
If this Pokemon is a Castform, its type changes to the current weather condition's type, except Sandstorm. This effect is prevented if this Pokemon is holding a Utility Umbrella and the weather is Rain or Sun.
Which Pokémon have Forecast?
1 Pokémon and forms can have Forecast: Castform.
Effect text from Pokémon Showdown (MIT); which Pokémon have it from Showdown's Pokédex, cross-checked against PokéAPI. Unofficial fan site.