Niantic, the game’s developer, said Wednesday that Pokémon characters from previous games Pokémon Ruby and Pokémon Sapphire will join the hit mobile game, which debuted in 2016.

Pokémon Go is known for incorporating augmented reality technology that lets players use their smartphones to see monsters overlaid on the physical world. Among some of the new Pokémon joining the same are the peculiarly named Treecko, Torchic, and Mudkip.

Despite the fun of chasing and capturing the new Pokémon, the most noteworthy addition to the game is its incorporation of real-world weather. When its raining outside, for example, players will be more likely to spot the Mudkip creatures that enjoy “splashing around,” Niantic said.

The ability for players to cast certain types of magic attacks will also be influenced by real world weather conditions. Casting a spell called Charizard’s Fire Spin, for example, will be more effective when it’s sunny outside.

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Niantic’s incorporation of real-life weather into Pokémon Go’s gameplay is an example of how its developers continue to push the boundaries of augmented reality. Developers routinely update the app with new augmented reality features that have helped to maintain the game’s popularity, despite concerns about AR’s long-term appeal.

Big tech companies like Apple, Microsoft, and Facebook all see AR as a potentially game-changing technology, but there has yet to be a big breakthrough AR app except for Pokémon Go.