All of the Pokémon in Pokémon Go require a small amount of candy to power up and go through their evolution cycle. You can earn this candy by walking with them as your buddy, capturing multiple versions of that Pokémon, trading them in, or completing weekly research tasks. Several Pokémon have additional evolutionary requirements, such as being evolved at night, using an item, or being near a module. There are select Pokémon that will require you to be next to a Rainy Lure module to hit their evolution.
At the time of this writing, the only Pokémon that can only use a Rainy Lure is Sliggoo into Goodra, a Dragon-type Pokémon. You can capture these Pokémon by catching a Goomy, but you have to be an extremely lucky trainer, which means there’s a low chance of encountering them in the wild.
The typical evolution for Sliggoo to become Goodra is just like this in traditional games, where you have to train it up to level 50, and then you have to wait to level it up again when it’s raining or foggy. Sliggoo is the only Pokémon that does this. There are no other Pokémon that level up through this method. We don’t know if developers Niantic are planning to add other Pokémon to this, and it might come up with a Pokémon from Sword or Shield or one from future games.
