After update 1.3.1 I noticed the constant sound of 'Thunder' in the background, as if it was getting ready to storm, or was storming. But this was happening All-The-Time, no matter where I was and even during cut scenes, and dialogue. Very annoying.
But after playing 'The Siege of Paris' (Trial by Fire), the constant 'thundering' in the background stopped. To be percise, it stopped after 'Trial by Fire'. Very odd. But, I did notice the 'Trail by Fire' had a cut scene where the queen was to be burned at the stake, and a very pronounced lightening/thunder storm occurred while the scene unfolded, even panning to the sky showing flashes of lightening.
Now, after that scene, the constant 'thunder' stopped.
I went on and tested other realms, also proving it had stopped across all over locations.
Just an observation I wanted to share, so if you are suffering from this bug, and have not reached that cut-scene yet, hopefully it will stop for you as well.