Niantic has announced that Regigigas is coming to five-star raids in Pokémon GO from Thursday, June 17th, 2021, at 10:00 a.m. to Sunday, June 20th, 2021, at 8:00 p.m. local time.

It’s a solstice surprise: Regigigas is coming to five-star raids!

Trainers, To celebrate the days getting longer in one hemisphere and the nights following suit in the other, Pokémon GO’s solstice-themed event is returning! Depending on which hemisphere you’re playing in, you’ll be able to encounter and catch different Pokémon during this event.

Date + Time
Thursday, June 17, 2021, at 10:00 a.m. to Sunday, June 20, 2021, at 8:00 p.m. local time

Features

• Regigigas is coming to five-star raids! From Thursday, June 17, 2021, at 10:00 a.m. to Thursday, July 1, 2021, at 10:00 a.m. local time, you can encounter Regigigas in five-star raids. If you’re lucky, you might encounter a Shiny one! Raid-related Field Research will also be available from PokéStops exclusively during this window.
• Trainers globally will be able to encounter Lunatone, Solrock, Spheal, and more in the wild. If you’re lucky, you might encounter Snorlax!
• Trainers in the northern hemisphere will be able to encounter the following Pokémon in the wild: Yanma, Chimchar, Summer Form Deerling, and more. If you’re lucky, you might find a Shiny Yanma!
• Trainers in the southern hemisphere will be able to encounter the following Pokémon in the wild: Snorunt, Snover, Winter Form Deerling, and more. If you’re lucky, you might encounter a Shiny Snorunt!
• The following Pokémon will be appearing in raids in the northern hemisphere: Alolan Marowak, Yanma, Petilil, and more.
• The following Pokémon will be appearing in raids in the southern hemisphere: Lapras, Piloswine, Snorunt, and more.
• The following Pokémon will be appearing in raids worldwide: Lunatone, Solrock, Klink, and more.
• Complete event-exclusive Field Research tasks to earn rewards like encounters with Yanma in the northern hemisphere, encounters with Snorunt in the southern hemisphere, and even Silver Pinap Berries if you’re lucky!
• Take a few snapshots for a surprise!

Bonuses

• Lunatone and Solrock will be appearing in the wild around the world during the event. Afterwards, Lunatone will be appearing exclusively in the eastern hemisphere, and Solrock will be appearing exclusively in the western hemisphere.
• Your Buddy will be eager to help you on your adventures! During the event, they’ll give you gift items and Poké Balls more frequently.
• The walking distance required to earn hearts with your buddy will be halved.

Please be aware of your surroundings and follow guidelines from local health authorities when playing Pokémon GO. Upcoming events are subject to change.

Source: https://pokemongolive.com/post/solstice-2021/