Humidity?

"What's humidity?" my girlfriend Rayna, from Texas, asks with SUCH innocence... I can't help but feel sorry for her in her naive state, since Texas didn't ever have humid heat. I hope she doesn't die in this air you can swim in, though i hear she's a good swimmer... so maybe she'll be ok? Everyone has been telling her how much she will hate it, and the poor girl's face every time someone says that... it's so sad. I wish to make the world a better place for my lady, though humidity is out of my hands. Sorry. Welcome to Illinois...