https://www.gamespot.com/articles/pokemon-go-june-2018-community-day-announced-featu/1100-6459131/

May's Pokemon Go Community Day may be over, but Niantic has already announced details for next month's event. The sixth Community Day will take place on Saturday, June 16, and it'll feature the rare Rock-type Pokemon Larvitar.

During the event, Larvitar will appear in much greater numbers than usual. Judging by the past few Community Days, players will need to evolve it into a Tyranitar before the event ends in order to learn a rare attack, although what move that will be remains to be seen; Niantic doesn't typically announce a Community Day's exclusive attack until just prior to the event.