Unless there is lightning within a certain mile radius, the rides will stay open. But if there IS lightning...the outdoor rides will close down until the storm passes.
Florida weathermen are usually wrong, but on your vacation, just trust them. Go to Universal on a rainy-looking day because all rides will be kept open in the rain as they're all mostly inside. If lightning comes, then the outdoor rides/shows; (JAWS, Curious George playground, Fievel's Playland, Woody Woodpecker roller coaster, Animal Actors, and Fear Factor) close until it's about three miles away.
At IOA, the only things open during lightning will be Spiderman, Cat in the Hat, and Poseidon's Fury walk-through show. If it's only raining though, all will be kept open, even the water rides (and during the rain, the water ride lines will be TINY)