"Was there a consensus of whether that was true or not"
Stan,
I can see where if conditions were right that cannon fire could affect local weather. Kind of like the "butterfly affect" has on huricaines. That starts as little eddies of disturbed air in the Shahiel Dessert that is just south of the Sarrah in Africa and as it moves off shore it picks up energy from the warm water and we know where that leads. In the same way, it seems to me and the turbulence that would or might be caused by cannon fire could grow to some strong wind and if conditions were right to seeding the clouds so that we had rain. NOt probable but yet possible I would think. I have seen storms pop up out of nowhere back in my flying days. One minute things are great and ten minutes later there is a level three or four or even five storm building in front of you.
FC