Team Rocket Balloons in Pokemon Go [duplicate]
Team Rocket balloons spawn every 6 hours. Specifically, one will spawn the first time you open the game after midnight, 6am, noon, and 6pm.
For the duration of the 4th Anniversary Go Fest Battle Challenge this was increased to every 3 hours, and for a short period on Sunday July 12th 2020 they were every 20 minutes.