Niantic has annnounced that a Cobalion and Lugia raids are returning to Raid Battles in Pokémon GO and for a longer amount of time.

Special Raid Weekends update—Cobalion and Lugia raids extended!

Trainers, Cobalion and Lugia are returning to Raid Battles in Pokémon GO! We want to make sure Trainers have enough time to challenge these Legendary Pokémon, so both will be available for a longer time in raids. Please note the change in schedule below.

Date + Time

• Cobalion will be available to challenge in Raid Battles from Tuesday, March 17, 2020, at 1:00 p.m. to Monday, March 23, 2020, at 1:00 p.m. PDT (GMT −7). You’ll also have a chance to encounter Cobalion as a GO Battle League reward encounter during this time!
• Lugia will be available to challenge in Raid Battles from Tuesday, March 24, 2020, at 1:00 p.m. to Tuesday, March 31, 2020, at 1:00 p.m. PDT (GMT −7). You’ll also have a chance to encounter Lugia as a GO Battle League reward encounter during this time!

Features

• Cobalion will know the event-exclusive attack Sacred Sword
• Lugia will know the event-exclusive attack Aeroblast
• If you are lucky, you might encounter Shiny Cobalion and Shiny Lugia!

Source: https://pokemongolive.com/en/post/cobalion-lugia-raid-events/

Updates to events: Lugia Raid Week

Trainers, The following events have been canceled, postponed, or changed.

• Lugia Raid Week: This event has been canceled.
• Raid Hour: This event has been canceled.

Source: https://pokemongolive.com/en/post/lugia-raid-weekend/