Please use the following guide:
Every time you change the loglevel, you have to restart openhab.
If you want to see even more in log, set the level to TRACE to also see the communication with the provider.
If you see nothing, then it could be that the binding is not installed.
To see if weather binding currently is installed, open karaf console and type in:
feature:list | grep Started
If you could not find the “weather” binding, then type in:
feature:install openhab-binding-weather