Legendary Week

Legendary Week was an event in Pokémon GO.

Features
During the event trainers had opportunity to catch all three Legendary Pokémon of Weather Trio, as for the time of the event Kyogre and Groudon had returned to the Raid Battles to be battled along with Rayquaza that was available at that time.

Moreover, if Rayquaza was defeated more than Kyogre and Groudon combined, Pokémon that typically prefer windy weather (for example, Bagon) would be more likely to hatch from Eggs from March to March. If not, Pokémon that prefer sunny or rainy weather (like Trapinch or Lotad) would be more likely to hatch.

Pokémon Eggs hatchlings
The results given on March, 2018, stated that Rayquaza was defeated more times than Kyogre and Groudon combined, which resulted with Pokémon preferring windy weather hatched from Eggs.

Following Pokémon were more probable to hatch from Eggs obtained between March to March, 2018:

Shop special offer
For the time of this event there were special promotional offer available from in-game shop with following item-bundles :

Promotional pictures
Following promotional pictures were published by creators of the game across their social media channels.

Trivia

 * On March, 2018, 52% of victories was in Legendary Raid Battles against Rayquaza, when 48% was combined victories against Kyogre and Groudon.