We are seeing it too

Happening to us too!

As of a few minutes ago it does seem that there is acknowledgement of the issue on the Apple Status page - https://www.apple.com/support/systemstatus/ Seems to be widespread as the weather app on my phone isn't really working either. Wish for a bit more stability, but it's nice to see at least an acknowledgement that there is an issue. 🥹

Yes, Darksky API shuts down today. The transition took us some time (you have to learn JWT generation if you haven't/there's some contract changes/etc.). I would maybe hold off or make other plans until Apple gives more details on the 5xx errrors, There's been a troubling lack of communication from engineers as you can see elsewhere on the weatherkit forums. It caused a lot of issues for us during implementation because we were concerned we were doing something wrong, but it was an API outage.