This month, Mankey are in Route 30, Gastly are in Union Cave and Stunky are in Goldenrod Tunnel !
UPDATE: As a trial, swarms will now be updated once every two months instead of one. This gives you more time to try and reach a swarm Pokemon if it is the next route over or if you are in a quest when swarms are announced.
It seems Johto is being visited by a rare variety of both Pidgey & Voltorb this Christmas season. Cherrygrove Streets are visited by the vibrant red birds whilst Goldenrod's Tunnels have a mix of the regular & this strange snowflaked Voltorb.
If you want a rare coloration of these pokémon make sure to head over quick before they disappear!
*Holiday Swarms available until the end of January.