The most important thing is to take him to the vet to rule out health issues - sometimes cats yowl at night because of pain, hyperthyroidism, or other problems you might not notice during the day. I know you say he seems fine, but certain issues aren't that easy to spot. Once you've ruled everything out, the behavior could be stress, boredom, or simply that your Persian has decided nighttime is the right moment to socialize (cats are funny that way).
In the meantime, try to tire him out more during the day - active play sessions before evening, especially around 7-8 PM, so maybe he sleeps when night comes. Persians are lazy by nature, but they still need stimulation. Then check if he has access to windows where he can hear other animals or nighttime noises - he might be excited by that. Some cats also yowl to seek attention, so if you ignore him but your neighbors complain and you're stressed anyway, he picks up on it and keeps going.
One last thing: if the vet rules out medical issues and play isn't enough, try giving him a more structured routine with food and play at the same times, maybe an evening snack that calms him down. There's also people who use pheromone diffusers (like Feliway), which sometimes helps. But really, the vet is the first step - don't risk spending months trying solutions when it could be something that's easily fixed.