https://www.gamespot.com/articles/pokemon-go-rotates-lunatone-and-solrock-for-summer/1100-6459976/

There's no better way to celebrate the longest day of the year than with region-specific Pokemon. As of the summer solstice, Hoenn's Rock and Psychic-types Lunatone and Solrock have swapped regions in Pokemon Go.

Lunatone, which resembles a moon, will now appear in the Americas and Africa. Lunatone originally appeared in Pokemon Ruby and Sapphire alongside Solrock. Solrock, the sunnier of the two, will now appear in Europe, Asia, and Australia.