Having a look at the pricing, the free teer has a limit of 60 requests/min (should be acceptable I guess) for the free teer and has access to the 5 days forecast. https://openweathermap.org/price
Dark Sky API might be an option, it's free for the first 1000 requests / day, not sure what it involves in creating an account yet, whether it asks for method of payment to be setup ahead, will see. https://darksky.net/dev/docs#forecast-request
We might want to look at the XBMC mainline plugins on weather, see what they did there and maybe pick one that works and make the appropriate foundation changes for supporting even the one plugin we choose as the source of information.
Would need some review to see how it was last implemented in XBMC4Xbox and try to get it closer to the "addon" model, even if not the full addon support for any Weather addon from XBMC mainline, even if one that is deployed as a plugin or a script. https://www.xbmc4xbox.org.uk/wiki/Weather
