Tactically apply baby powder around the unmentionables and and then wrap ice cubes in a hankerchief or bandana and wrap that around your neck, with the ice resting on the back of your neck. Those two steps pretty much prevent me from becoming a monster when i go to Bonnaroo year-in-year-out.
There's plenty of places in the U.S. where 100% humidity is not uncommon. Right here in Houston, TX, for one. The problem here is that even with saturated air we're still very drought prone which tends to create a feedback loop of hotter temperatures. The heat index can be 118F in the middle of summer with 100% humidity and not a cloud in the sky.
The best part is when it feels like a 1/4 cup of water has been dumped into your pants right around the asshole so you've got water sloshing all over the place down there.
I've lived in Texas, Florida and the carribean. I travel the states, europe and latam for work. The humidity isn't that bad. I went to basic training in san antonio and ran outside. It gets hot. You drink lots of water and move on.