The rides do not close due to rain.
We have been on them like drowned rats, when there was over an inch of water to wade through to get to them. They are verified for all bar - lighting (for obvious reasons) and temps below 45F - Over winter there are several days when they cannot start running until temps climb, and on a few days are off pretty much all day.
At universal all indoor rides usualy continue in a thunder storm, unless so bad that there are power outages, or tornado warings, and you will know that if it happens daylight to darkness in mins and I can assure you that a ride will be the last thing on your mind.
I know its bad when the weather is not what you want (camping in france last july- uggh) but you have to try and make the most of it.
Try going to unusal places for diners- Sci fi, san angelos, trex, rainforest and sanna are good for kids and tepan edo ragglan rd, bongo for older teens. also do disney quest and tour some delux hotels esp animal kindom as they can animal spot from inside or at sanna's
At universal older teens/young adults can chill out at margaretaviles and a must do for this age is the back tour of the hard rock cafe - free (but we gave good tips as the guide was great and the 1.5hr tour was the highlight of my eldest dd holiday).
Go into to the parks in a very light outfit, incl flip flops do the water rides then change into dry clothes at nearest piont to show or resturant you plan to visit. (take ziploc bags for the wet stuff) then do some indoor shows - lion king, nemo, beauty, and drawing with an imagineer, follow that with the indoor rides, then back into the wet stuff to redo water rides- we have gotten to stay on time and time again in weather like that- then its back into the dry stuff - on really bad days take 2 sets of dry, one for the journey home.
To those not there yet, do not go already down about it as that will set the tone for your hols- start working on wet day plans- I'm in the same boat as we are due to go the end on of june- but there is no way some water is ruining my trip - I am pulling together my wet day plans and packing water proofs!

Hope you manage to conjur up some fun even if its in the rain
oops forgot - always take a few very small hand towels (golfy things or those very thin ultra absorbent camping ones) one to dry seats and the others to dry legs when you get inside.