As per #47 explains, DarkSky.net has been acquired by Apple, who plans to absorb the company and close up the APIs "by the end of 2021" (relevant announcement).

This means forecast.el needs to be rewritten using a new, preferably more open data provider. This is also an opportunity to detach forecast.el frontend and backend so that backends can be switched if new ones are implemented later. Maybe use EIEIO?

Candidates for the new backend:

• OpenWeatherMap (https://openweathermap.org/)
• MAAS (http://ingenology.github.io/mars_weather_api/) (why not, as an option)
• Wttr.in? I think they have a JSON api

Some additional ideas:

• Use geoclue.el for setting lat&long? (see this)

Alternatives for forecast.el (Apple will apply a new privacy policy):

• sunshine.el: uses OpenWeatherMap, less detailed but more beautiful than forecast.el
• noaa.el: uses data from US Govt's National Atmospheric and Oceanic Administration, which is seemingly limited to the USA
• weather-metno.el: Uses data from Norwegian Meteorologisk institutt which provides data for all world under a Creative Commons licence (e.g. see Istanbul)
• emacs-wttrin: A simple wrapper around https://wttr.in which also supports JSON output (thus potential backend, see this)
• yandex-weather.el: Gets data from Yandex.Weather