The weather widget updates when it loops in some way ie when the whole layout reloads, when there is more than one widget in the region and so the weather widget reloads when player cycles through them or if the region with single weather widget is set to loop or if you make changes to the layout which will also promot it to reload.
Which means that if you have an overlay layout with only weather widget in the region, then it will not reload itself, so it will not update itself either.
In this case, you can set the region with weather widget to loop (layout designer, region options, loop)
or add second widget to the region.
Then it should update just fine.