Disney has their own meteorologists. They keep rides open as long as it is safe for guests to ride. Enjoy watching lightening in the distance as they will shut down rides when the storm gets closer.
When it's raining, the parks will be slower and you will be able to knock out a lot of rides.
Rain storms are typically short so try and take in a show during the storm to avoid the down pour.
avoid cotton shirts
freeze towels the night before and put them in a zip lock bag so you can use them the next day.
wear sandals more than tennis shoes
make sure to have 2 pairs of tennis shoes in case one pair gets wet from rain.
wearable fans are common throughout the park
Use the cooling towels
Disney World is probably the safest place to be during the a Hurricane. Disney has their own back up generators for the resorts and will make sure to provide enterainment and meals for those who are staying at the hotel. Unfortunately, parks will close the day the hurricane hits the area.
I have been there when there was a potential hurricane. We had lots of rain, all day, everyday and had a wonderful time.