The weather widget isn't showing for me in Opera GX. In regular Opera (Opera One), it's showing, but I can't set a location (manually or via automatic detection). The agree button doesn't do anything, the autocomplete for the location field in manual location setup isn't working and the save button is grayed out. It's like that in older version of Opera too where I'm sure the weather widget worked.
So, for me, it seems like it's something with the service itself (Opera's servers that provide the weather api or something).
So, for now, I would definite goto the URL opera://settings/startPage and disable weather since it's not working and since the animated gif that shows by default uses a tad bit of CPU.