The official Pokémon website has announced that players of Pokémon Sword and Pokémon Shield can encounter Seaking, Pinsir, Heracross, Ninjask, Fan Rotom, and Vanilluxe more frequently in Max Raid Battles from August 6th, 2021 until August 8th, 2021, at 4:59 p.m. PDT.

Encounter Pinsir, Heracross, Ninjask, Fan Rotom, and More in Max Raid Battles

Summertime in Galar brings cool Pokémon to Pokémon Sword and Pokémon Shield’s Pokémon Dens, including Shiny Vanilluxe.

Things are heating up as summer arrives in the Galar region. Until August 8, 2021, at 4:59 p.m. PDT, Seaking, Pinsir, Heracross, Ninjask, Fan Rotom, and Vanilluxe will appear more frequently in Pokémon Sword and Pokémon Shield's Max Raid Battles. Very rarely, a Shiny Vanilluxe may also appear. Get ready to take part is some heated battles!

For an opportunity to encounter these Pokémon in a Max Raid Battle, you'll need to connect your Nintendo Switch system to the internet through Y-Comm or by selecting Mystery Gift in the X menu, then selecting Get the Wild Area News. After that, whenever you see a pillar of light shining from a Pokémon Den, you can walk up to the Pokémon Den and interact with it to start a Max Raid Battle with a Dynamax Pokémon. This event does not affect the Pokémon encountered within Dynamax Adventures.

Source: https://www.pokemon.com/us/pokemon-news/encounter-pinsir-heracross-ninjask-fan-rotom-and-more-in-max-raid-battles/