The official Pokémon Scarlet and Violet website has announced that Chansey will be appearing in mass outbreaks throughout the Paldea region from Friday, November 29th, 2024 to Sunday, January 5th, 2025, at 23:59 UTC.

Prepare to Level Up with Mass Outbreaks of Chansey!

Seek Out Lots of Chansey and Train Up Your Party! Get ready to take a chance on Chansey! From Friday, November 29, 2024, at 00:00 UTC to Sunday, January 5, 2025, at 23:59 UTC, Chansey will be appearing in mass outbreaks throughout the Paldea region. Defeating these Chansey will yield lots of Exp. Points, so use this opportunity to train up the Pokémon in your party and prepare for the Shiny Rayquaza Tera Raid Battle event starting Friday, December 20!

Event Schedule

Friday, November 29, 2024, at 00:00 UTC to Sunday, January 5, 2025, at 23:59 UTC

Featured Pokémon

Chansey

Location

Paldea

What Is a Mass Outbreak?

Mass outbreaks are a phenomenon in which many of the same species of Pokémon appear in one location. During limited-time mass outbreak events, certain Pokémon will become more likely to appear.

Information about Mass Outbreak Events

• In order to participate in limited-time mass outbreak events, you need to have downloaded the latest update data and the latest Poké Portal News. You do not need a paid Nintendo Switch Online membership to receive the latest Poké Portal News.
• You can download the latest Poké Portal News by selecting Poké Portal from the X menu, then Mystery Gift, then Check Poké Portal News.

Source: https://sv-news.pokemon.co.jp/en/page/287.html