Third party developer Yo-han offers a World Weather Online iOS library on Github. To implement, users can check the test project. To build the library, users can call the build.sh script in the root file. With instructions, resources, and tools offered by the third party and World Weather Online, developers could complete the integration of weather features in mobile applications.
Popular weather data site Weather Underground (Wunderground) has a new version of its Weather Underground API and two things are notable: its former XML service is being phased out in favor of JSON. And it has a very clear pricing structure, though there's a free version for non-commercial projects.