Driving over the moors the sky looked quite ominous in the distance. There seemed to be quite a storm going on.
We have a local saying here, "it's black over Bill's mothers" whenever dark clouds loomed. I'm not sure where the saying originated from and no idea who Bill is or his mother. Some believe that "Bill" is a reference to the playwright, William Shakespeare.
Or it could it be about Kaiser Wilhelm II, who was the last German emperor and King of Prussia. Apparently, Germany's foreign policy during World War 2 was similar to Wilhelm's personality, unpredictable and stormy. Source I'm not sure the meaning is that sophisticated. I expect it is about some bloke and his mother who lived down the road!
As kids, we used to count how many seconds between the lightning and the sound of thunder to work out how many miles away the lightning was. It's probably not that simple, but it was good fun.
I was a bit envious of people in the middle of this, as I love a good storm, especially thunder and lightning as long as I'm undercover. Apparently, I am a ceraunophile! Source
We stuck around for a while until the storm passed. It was quite a show.