Hey Peter Ryan,
We'd recommend reviewing the information in this article: About privacy and Location Services in iOS and iPadOS
As the Weather app uses location services, an issue there could be contributing to the behavior you're seeing. Ensuring your Location services are set up as expected for the Weather app could help to resolve the issue.
"Give apps permission to use your location
The first time an app tries to access your location, it must ask for your permission. You see a prompt explaining which app is asking for permission to use your location as well as the app developer's reason for requesting it.

Some apps ask to use your location only while the app is in use. An app is considered "in use" when you’re actively using it in the foreground, or when it is using location in the background, in which case a blue pill will display in your status bar.
If you grant an app While In Use permission, the app may ask you for permission to use your location when it is in the background.
When you allow an app to use your location in the background, your device will remind you from time to time that an app is using your location, and will display those locations on a map. You'll also be asked if you want to continue to allow the app to use your location in the background."
Thanks!