Looks like wttr.in forks wego which uses these sources [0]:
* worldweatheronline.com
* darksky.net
* openweathermap.com
I couldn't find anything more concrete.
But what is used as source of a weather data?
FTR, I'm using OpenWeatherMap via `$ weather.sh`[0], but its output has issues & still needs to be polished.
[0] https://github.com/uriel1998/weather.sh