I’m from the Deep South. You couldn’t tell by my accent. I moved away for college and lived overseas and on both coasts. I didn’t know what a “sun shower” was until I was in my mid/late twenties and said “the devil is beating his wife” in front of my friends. That’s the only term for it I had ever heard up to that point.
I grew up in the CA bay area and always called them sunshowers. I didn't make that up: I called them sunshowers when I was a kid because the people around me called them sunshowers.
As an aside, I also taught linguistics at the university level for about 10 years. I do question the accuracy of many of Katz's charts because they very often do not match people's expectations, and beyond the level of "you expected this because you didn't know any better". I would take them with a grain of salt. That's not really a dig on Katz, either: difficult to study anything at this scale.
Funny, but we use the same thing about the Devil beating his wife in Romania as well. At least in Transylvania we do. It's surprising to see this being used in the US as well. I wonder where it originated from.
Grew up in Georgia. My mom would refer to it as the devil beating his wife. She got it from her mom who presumably got it from her parents. I have no idea why that expression, never got an answer for that.
I've mostly heard some variation on sunshower in Texas because while they're not common, they're not super rare either. We also rarely get "sun-derstorms" (dunno what else to call it) in Texas.
It happens very frequently in Florida, I know of it as a sunshower. It not unheard of for your FoV to be filled with blue sky but it's actively raining... that is when people mention sunshower. I've heard the devil is beating his wife but only rarely.