The Dark Sky API, which was acquired by Apple in 2020, is no longer accepting new signups and will be deprecated until the end of 2021. Existing users are encouraged to switch to alternative APIs like AerisWeather. AerisWeather offers similar functionality to Dark Sky and provides detailed documentation to help developers transition their applications. The process of transitioning from Dark Sky to AerisWeather involves setting up a RapidAPI account, subscribing to AerisWeather, changing the base URL, identifying endpoints to update, and testing the API. Developers can use code snippets or generate their own on RapidAPI in their preferred language to integrate AerisWeather into their applications.