Swollen lug nuts? What?

It absolutely happens in the lower states. I was a supervisor in the tire center at Costco for 7 years in locations from San Diego CA to Round Rock TX. It happens everywhere.
I've never even heard of it until this thread and just assumed it was a rust belt issue. The only problem I've had with them is the dang caps coming off. Both of my mid 90's Dakotas had them but they both now wear the solid lug nuts that are chromed. Same thing got put on my 97 diesel when I put Hummer H2 chrome plated alloy wheels on it many years ago.