Hmm, AK in the rain? I think I can talk about that!
OK, I admit we purposefully posed that shot to look miserable, but that was at the end of about 4 hours of mostly heavy rain in the park. We ended up cutting out pretty early.
Definitely the worst park for bad weather. We didn't have a choice, though. We were on our last full park day, and had only had an afternoon at AK.
We rode the safari in the AM, then did FotLK. Then we headed over to do Flights of Wonder, which DD an DW did while I rode Expedition Everest. This was NOT fun at all. The ride goes inside and outside frequently, so you would move outside and be pummeled with rain for 10 seconds, completely blinding you.
After that we left. (And understand we LOVE AK, so this was very disappointing to us.)
My first choice would be to switch to another park if you can. If that's too hard, understand you will be able to see the shows (we had already seen the Nemo Musical the previous 1/2 day), the Safari, and Dinosaur. I suppose you could also take the train out to Conservation Station. The animals do come out more, but looking at them in the pouring rain isn't much fun.
We had some friends we were supposed to be meeting that we missed out on that day, but they showed up at the park after we left. They said once the rain stopped, the crowds were non-existant and they rode EE six times with no wait. So it really is a tough call what to do.
If I could've switched, my first park of choice on a rainy day would be Epcot Future World, then MK (only because the rain keeps the crowds away) then HS (more indoor than MK, but I think you see the opposite effect on a rainy day - more crowds).
That said, at EIGHT days out, I wouldn't sweat it just yet. Heck, I would barely think about it 2 days before. The forecasters in Florida don't have any more of a clue than anywhere else. Probably even less because they have those crazy "pop-up" Thunderstorms, so it can be a downpour in one park while the other one is dry.