In 2000 I was in basic training in South Carolina. I'm from California and my battle buddy was from Hawaii. One day it's snowed and my buddy left formation and ran around catching flakes with his tongue.
Drill sergeant just let him do it. It's the only time I've seen someone get away with something in front of drill sergeant.
I think they're saying in super hot tropical regions generations could pass without freezing temperatures. I don't know enough about the weather in tropical regions to know if that's true or not. Maybe like equatorial regions? Or the Seminole people in Florida? But I think trade with other regions and migration might throw that theory off.