Usually just portions - and you may have rain at MGM but not at AK, or at the resort but not a the park you're going to. Of course, there can be the non-stop days as well. Bring parkas, and remember how light the crowds will be if it rains! It cools the place down as well, and there's always plenty to do in the rain at WDW. Also - the weather around there just isn't too easy to forecast - until the night before or the day of - it will change constantly. We were supposed to get a lot of rain on our trip, and we got one tiny light shower at AK in the 8 days we were there! I'm sure you'll have a great vacation!
