How to get a shiny rayquaza
The Hoenn Celebration Event is far from the first event to offer Rayquaza to Pokémon Go players, with even the shiny version being available in the past as well. However, the actual chances of getting a shine in one look are the highest they've ever been, but you only get one chance.
This is because Shiny Rayquaza is not part of this week's raids, but rather the timed search for the Hoenn Celebration Event that is currently taking place. For this next week, the other two main legendaries of the Hoenn region are going to be in the five star raids, which are Groudon and Kyogre. For Rayquaza, though, you're going to have to do some work, including ending some of those raids.
As part of the timed search, you have tasks to complete which you can read in this specific guide. It is also not a multi-part search, as you only need to complete all three tasks to complete it. Once you do, you will be rewarded not only with a Silver Pinap Berry and 3000 XP, but also an encounter with Rayquaza. This is no ordinary Rayquaza, however, as it comes with the exclusive charged Hurricane attack.
What makes this encounter better than usual for getting a shiny Rayquaza is that the special research related shine rates are improved over the norm. Technically you have a better chance of getting a shiny when Rayquaza is raiding since you can keep doing them until you get one. However, the unique chance you get to complete the Timed Research of the Hoenn Celebration Event has a higher than usual chance of getting the elusive Shiny Rayquaza.
