We've had a week or more of thunder storms here in Southport, and a couple of nights ago a lighting bolt hit a neighbor's air conditioning unit and fried it (I think I can identify the particular strike; it was a deafening triple boom, like a high-powered rifle being fired three times in rapid succession).
This evening, while Mrs. Paco was discussing the weather with another neighbor, the lady mentioned a phenomenon that I've never heard of: something called "Seneca guns". They are loud booms that have no proven source, but are apparently fairly common along the eastern coast. Speculation is that they are the result of either minor seismic events or strange doings in the atmosphere. Here is some additional detail.
If this were a very recent phenomenon, I'd guess it might simply have been me firing one of my .41 Magnums with hunting loads over at Ye Olde Shooting Range, but stories of the booms go back to the mid-19th century, at least.