The issue was resolved after about 8 hours for me as well. No code changed on our side, this seems to have been a WeatherKit issue.
During this whole time the Apple System Status page continued to be green: https://www.apple.com/support/systemstatus/
I'm not sure this status page can be trusted. How come a service issue that affected multiple customers didn't cause the dashboard to be yellow or red during the time it was broken?