@MarkNagy thank you for the advices. I tried to set location to a favourite location instead of current location, and waited several hours but the issue persists. I still need to have it slightly narrower to have the widget working.
The nova launcher allows quite customised home screen grid width setting, mine is set with a 5x5 grid, with subgrid, meaning that it's like a 9x9.
I don't know how windy fetched data for widgets, but my guess is that, when the hourly widget is wider it wants to display more hours forecast, and it tries to fetch data for a longer period of time and the server is limited somehow in is response and therefore the widget sees incomplete data to fill the period of time it wants to display completely... Just guessing.
Regards