Dark Sky has announced that they have been acquired by Apple and this acquisition has implications for the Fantastic Weather plugin. Apple is not allowing any new API sign-ups, so at this point it will not be possible for new users to install the plugin. Existing users should be supported through the end of 2021, when the API will be sun setted. I will do my best to fix any bugs in the plugin during this time, but probably won't be developing any new features going forward.
EDIT: Dark Sky have now reported that existing customers will be supported through the end of 2022.