Fetching weather data from the OpenWeatherMap API
I would suggest splitting this into two classes, one being your CityWeather POJO and a separate class for performing the logic currently in CityWeather.  The primary reason for this is to separate the business logic here (the parsing of the response from OpenWeatherMap) and your representation of the response (CityWeather).  In doing so, whichever class you have that is currently invoking the call to OpenWeatherMap should then pass the OpenWeatherMapResponse response that is returned from the call to this new class, which we'll call OpenWeatherMapParser.  OpenWeatherMapParser should take this response, and instantiate CityWeather objects based on the logic you currently have in CityWeather by calling it's setter methods