New Gen 3 Pokémon rolled into Pokémon GO recently, and with them a few new regional exclusives: monsters that can only be caught in certain parts of the world. Africa now has its first creature in the form of Tropius, which spawns throughout the continent and parts of the middle east. We've also got Illumise and Volbeat, which follow a similar worldwide division as Zangoose and Seviper and might also rotate in the same way. But there's one in particular that I'm interested in today, and that's Castform, which changes between sunny, rainy, snowy and normal forms based on the weather. Specifically, I want to talk about Snowy Castform.
On its face, Snowy Castform is not a regional exclusive. It could occur anywhere in the world if it's snowing, which naturally means that it can't occur anywhere in the world. There are a ton of places in the world that get no snow, ever, and plenty more that get only get it once every few years, or maybe once a year or so. If that was all we were dealing with, Snowy Castform could easily be considered a fairly straightforward regional exclusive.
But Niantic has a solution to this problem: Snowy Castform is also available in fog, which is a more equitably distributed meteorological resource than snow. In the past day or so I've gone down the rabbit hole in trying to figure out relative worldwide fog prevalence, which is a tricky question with two parts: the first is figuring out to what degree fog forms in different places, the second is figuring out to what degree fog shows up in the weather data that inform Pokémon GO. On an anecdotal level, I have yet to see fog appear in the game since the weather system debuted, and Reddit comments would seem to suggest I'm not alone.
Let's take Las Vegas, for example which gets so little snowfall that we can say it gets none, at least from a Pokémon GO perspective. And it only appears to get a negligible number days with fog a year, and it's hard to tell whether or not those days would be enough to trigger the Fog event in Pokémon GO. Phoenix, too, gets little fog and effectively no snow. In places like that, of course, Rainy Castform could be just as much of a prize. On the other end of the humidity spectrum would be Miami, which obviously gets no snow but where fog is also rare due to the relative lack of temperature differentials in the tropics. Again: rare, but not unheard of.
Another candidate I had for places with little access to Snowy Castform was Rome, which seems from the amount of research I've been able to do get very little fog, though I'd be happy to hear any more information on this subject on Twitter. Even a place like London would have fairly limited access to Snowy Castform despite stereotypes formed by the smog-choked streets of the Victorian era.
Fog is often a byproduct of temperature differentials between the land -- or water -- and the air, and so in many places where fog does occur, it might be for brief periods early in the morning. This could easily be considered a feature, and not a bug: I like the idea of setting the alarm for a pre-dawn Castform hunt.
Again, we're not just talking about fog in a strict sense here: we're talking about the level of fog that defines the forecast to the point where the the little icon reads: "fog." Mist was hardly uncommon when I was living in New Orleans, particularly during hazy summer nights, and yet I can't remember seeing a "fog" icon on the forecast. It's no coincidence that this game is developed in San Francisco, where fog is as regular and well-defined a weather event as sun is elsewhere. It's for this reason that we'll need a bit of Silph Road data over time to determine the degree to which certain places around the world actually wind up being able to catch Snowy Castform, and where anecdotal information actually becomes important. Like I said, I've never seen fog in the game, and other people seem to have had a similar experience elsewhere.
It would seem to add up to Snowy Castform being a very rare Pokémon in many places worldwide, but not in the way that other Pokémon have been. It's a rare Pokémon that nonetheless has specific conditions for spawning, meaning that you can seek it out more specifically than you can, say, Chansey. Creatures like Chansey can be annoying because there's no way to seek them out or predict when you might get them, leaving you at the mercy of capricious RNG. That's not the case for Snowy Castform, which has well-defined criteria for spawning. It's that connection to real-world weather creates a real sense of where Castform "lives" and doesn't, which is at the heart of the Pokémon in the real world concept. Those places where snow or fog are rare might be the best places to catch the thing, because it would be that much more special when it happened.