Pokémon Go Fest: Seattle global event guide
Pokémon Go players not attending Go Fest: Seattle can still take part of a Collection Challenge at home and catch Clamperl, which has a boosted spawn rate.
This article references relevant content from the polygon.com website. Original article link: [https://www.polygon.com/pokemon-go-guide/23274587/go-fest-seattle-oasis-habitat-collection-challenge-clamperl]

Pokémon Go Fest: Seattle is an in-person event, but players at home can still take advantage of a very small version of it. From July 22-24, all Pokémon Go players will have access to slightly different spawns and a Collection Challenge.
All the Pokémon required in the Collection Challenge also have a boosted spawn rate.
Most valuably, the event boosts the spawn rate of Clamperl, which is a pretty rare spawn outside of events. The Collection Challenge also rewards Panpour, which is a regional Pokémon. Those not living in The Americas or Greenland will definitely want to grab one before the Collection Challenge ends.
GO Fest Seattle: The Oasis Habitat Collection Challenge
Catch the following for a reward:
Reward: 2,022 Stardust, Panpour encounter, 2 Pinap Berries