For the most part (and yes there are exceptions due to frontal systems, etc) it does not rain all day - we will get the afternoon/evening storms that come and go.
Due to sea breezes it is rare the this time of the year that you would not see scattered/isolated T-storms in the forecast.
I am right now watching "Local on the 8's" on the Weather Channel - and it is pretty normal - mid to upper 80's - chance of T-storms every day for the next 7 days. The mid to upper 80s is a nice change from the lower to mid 90s we have been having! It is 77 now with 88% humidity and not a cloud in the beautiful blue sky, by mid day, I would expect to start to see the clouds forming!
Yesterday we had a storm that lasted about 1 to 1 1/2 hours - rain heavy at times, light at others, but by 2:30 it had cleared and the rest of the day was beautiful. On Saturday we had the same mid afternoon, DD and I headed to MK around 7pm, and it was a beautiful night.
DD and I were at MK last Sunday and it rained hard for about 1 hour (she rode Goofy's Barnstormer 8 times in a row and was SOAKED - but had a great time). They did close rides for about 45 min or so later when the lightning was close to the area.
Rain at Disney does not generally ruin a whole day, but bring your ponchos just in case!!!
(PS - I am a PA Native (Lansdale) relocated to Orlando 3 years ago!)