https://www.gamespot.com/articles/heres-what-pokemon-go-bonuses-are-coming-after-leg/1100-6457162/

Legendary Week is now over in Pokemon Go, and Niantic has shared the results from the 10-day-long event. The company revealed that players managed to defeat the Legendary Pokemon Rayquaza more times than the returning Groudon and Kyogre, which means Pokemon that like windy weather will be a lot more common in the game for the next few days.

From now until March 16, Pokemon that typically spawn in windy conditions, such as Bagon, will be more likely to hatch from Eggs. In addition to that, Raid Battles will likewise feature Pokemon that prefer windy weather. Players will also receive double XP as an added bonus from now until March 16.