If you have access to an Apple developer account I would use the [WeatherKit REST API]. It's very similar to the Dark Sky API. (Presumably designed by the same devs). I'm going to ask one of my friends for an API key for their unused free quota.

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/

API wise I like and use PirateWeather[0]. Don't know if they have a front end but the API has been stable, reliable, and accurate.

[0] https://docs.pirateweather.net/en/latest/API/

Often the national service will provide an api as a public good. Ex: https://www.weather.gov/documentation/services-web-api

It really depends on where in the world you are. I always suggest using local data if possible as nothing comes close to local domain knowledge.

But here are some suggestions:

https://open-meteo.com/ (straight from the models)

https://openweathermap.org/

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.

Yr.no and met.no are great. It’s more data if you are interested in the Norwegian area.