We went last year in the pouring rain. The tour went on as scheduled except that HMH was acting up when we went to get on so we skipped it and the parade wasn't able to go on so we stood and watched the brief character calvacade instead. They gave our family of four 8 fastpasses to be used on any ride. The FPs were good through the end of the following day. We used them for Finding Nemo and Peter Pan. Since we'd already been on HMH with fastpasses a couLe of times that visit, we thought this was a great perk.
I was bummed we didn't get our special seats for the parade. When we checked in at the guided tour kiosk earlier in the day, they did offer to let us change to another time slot if one was available. We were leaving at noonish the following day (which was sunny, of course!), but we seriously considered changing to he earlier time slot on our day. We took the chance that the weather report would be accurate and the rain would continue and then slow to a small drizzle by evening. Instead, it cleared up for the afternoon saving every drop for a two hour downpour later in the evening.
I'll never forget that tour! Despite the cold and the wet, we all had a good time. Good enough that my now eight year old DD asked if we could do it again on our daytrip on Tuesday! The rest of our extended family going with us were pretty "meh" on the idea, so we aren't doing it this time. Just as well since once in the rain was memorable, but twice in the rain might be just a bit too much to ask of even the most dedicated Disney lovers.
Sooooo many puddles every where you walk. 
