Pokemon originally discovered in the Hoenn region will take over wild encounters until February 13

February 9th: New wave of Hoenn Pokemon + Rayquaza appears. Hoenn Pokemon will start dominating encounters. New Raid bosses appear. 6 hour lures start. Shop boxes appear.
February 13th: Hoenn Pokemon no longer dominating spawns.
February 14th: Kyogre leaves (presumably 1pm PST).
February 23rd: boxes end. 6 hour lures end.
March 16th: Rayquaza goes away.
https://pokemongolive.com/post/hoenn-pokemon-020818/