How to change the weather in Pokémon Pokopia
via polygon.com
Short excerpt below. Read at the original source.
If you want to change the weather in Pokémon Pokopia from rainy to sunny (or vice versa), you can use certain habitats and Pokémon to do so. Changing the weather has its benefits, as rain will rehydrate dry grass and some Pokémon require specific weather conditions to move into habitats.