OpenWeather's [One Call API] is almost a drop-in replacement for the DarkSky API. There are a few minor differences.
[Open-Meteo] is another really good API. Unfortunately it doesn't have the "minutely" forecast data, which I find really useful. (Is it going to start raining in the next few minutes? When will it stop?)
[WeatherKit REST API]: https://developer.apple.com/documentation/weatherkitrestapi
[One Call API]: https://openweathermap.org/darksky-openweather-3
[Open-Meteo]: https://open-meteo.com/
But here are some suggestions:
https://open-meteo.com/ (straight from the models)
Depending on how much detail you want, you might even just want to download XyGrib (https://github.com/opengribs/XyGrib/) and download models for your area.