In the month of February, you can find and battle Giovanni, the boss of Team GO Rocket, to rescue Shadow Raikou.
Tracking down Giovanni requires completing the Special Research ‘A Professor’s Work is Never Done’ to obtain the Super Rocket Radar. The Super Rocket Radar will allow you to find potential PokéStop where Giovanni is hiding out. Some of them might be Decoy Grunts so it might not be a simple task. After you challenge and defeat him, you’ll have the opportunity to capture a Shadow Legendary. This month he will have Shadow Raikou in his party.
Encounter Shadow Raikou!