This is an on/off type situation. It isn't the widget itself, it's the Internet feed from whatever service provides it to each widget. I have 3 weather widgets on my computer and one is working right now. The other two were working last week when I last checked, but 3 weeks ago there was a similar topic to this because the Apple widget was not working (but my other two were).
So don't expect a system update to do anything, particularly since the classic widgets are being deprecated.
Accuweather.com is working right now but not Apple's, or Weather Underground.