We went to WDW the last week of September, 2002. We had rain everyday due to a hurricane out in the gulf that was sending in bands of rain. We knew about the rain, but refused to let it stop us.
We stocked up on 2 for a $1 rain ponchos at the Dollar Tree. We took everything in the backpack inside a ziplock bag. We scotchgarded the backpack with an entire can of the stuff. We took a clean shirt and clean socks for each of us, just in case.....and yes, it saved us a couple of times. We took a couple of different sets of sneaks and a pair of sandals each. We purchased many bottles of water and powerade. We used our personal fans quite a bit.
And even with the rain, the increased humidity, and the constant need to be drinking something to stay hydrated, it was still be best vacation that I have ever been on in my lifetime. Go and have fun! Mickey