Weather widget not working.

There is a weather tool that you can enable via System Preferences : Extensions : Today : [√] Weather. You will find a calendar and calculator tool there too. These are not Dashboard widgets, but rather intended as functional replacements that appear in the Today section of the Notifications panel.

Mine hasn't been working for quite a while and even before that it was on and off for over the past few years. Presumably the server providing the data to that particular widget version is slowly being abandoned and this is it.

In Catalina, Apple has dropped widget/Dashboard entirely.

I have weather widgets from Apple, Weather Underground, and Accuweather.com. The last one is the only one that has been reporting any data for the past couple of months, and for the past few years the Apple one has been etremely sporadic and not at all for the past couple of months.