From 6 PM – 7 PM tonight, June 7th, not only will you be able to find Azelf, Mesprit, and Uxie in their respective regions, but Raid Invites from those regions will let you battle the Lake Trio from home… but remember, only five times a day.

Source: https://bleedingcool.com/games/tonight-is-the-first-lake-trio-raid-hour-of-the-season-in-pokemon-go/

Shortly after players discovered that had decreased the Shiny encounter rate for the Lake Trio Uxie, Mesprit, and Azelf, Niantic confirmed that it was due to a "technical issue" and promised that a fix was coming.

Source: https://comicbook.com/gaming/news/pokemon-go-shiny-legendary-raid-nerf-lake-trio/