Pokemon Go players have a new challenge: finding all four versions of the weather-related Pokemon Castform.
Last week, Pokemon Go added a wave of new Pokemon to the game, including the unique Pokemon Castform. Castform has four different forms, each of which are a different Type. Castform is by default a Normal-Type Pokemon, but it becomes a Fire-Type Pokemon when in its "Sunny Form", a Water-Type Pokemon when in its "Rainy Form" and an Ice-Type Pokemon when in its Snowy Form.
In the main series games, Castform changes forms depending on the weather. However, in Pokemon Go, a Castform doesn't change forms after you catch it. That means that a Normal-Type Castform will stay a Normal-Type during any kind of weather.
If you want all four types of Castform in your collection, you'll need to pay attention to the weather. Please note that once a Castform spawns, it won't change forms even if the weather changes, so if you see a Castform on your nearby tracker, don't expect it to change forms once it starts raining.
Here's the weather patterns that will trigger certain Castform spawns:
Normal Form: Cloudy Weather, Partly Cloudy Weather
Sunny Form: Sunny Weather, Clear Weather, Windy Weather
Rainy Form: Rainy Weather
Snowy Form: Snowy Weather, Foggy Weather
The good news is that Pokemon Go has made most of the forms available in different types of weather to make them easier to find. While parts of the southern United States don't get a lot of snow, they might have a little more luck finding an area with foggy weather to get that Snowy Form Castform.
Of course - there's no reason that players NEED to get all four Castform forms. Castform isn't a particularly strong Pokemon that would have any usefulness in gyms and players won't get XP for collecting all four of its forms. The only reason to get all four versions of Castform is if you're a completionist that likes having one of every available type of Pokemon in Pokemon Go.