I, too, was surprised how busy the park was in the rain this Saturday. Of course, it was Saturday and not Wednesday...but the park seemed more crowded than it had been on Wednesday and Thursday, despite the rain.
Some ride times were very low, though. Our Fastpasses were completely useless--for Indy, it was raining so hard, they just routed standby and non-standby through the covered area of the queue just the same (even though they took our Fastpass). We cursed them for showing human compassion

and then didn't use Fastpass for that again. For Space Mountain I think we got in line right when it came back from being down? So they didn't take our Fastpasses (the second time this trip!) but just waved us through the Fastpass line.

Soarin', they still had Fastpass distribution going in the evening, I think, but there was no Fastpass line going; everyone was in through the same line and all. Haunted Mansion Holiday didn't even offer Fastpass.
We left
Disneyland around 6 (maybe a little before) and there were an awful lot of people lined up for the parade, even though it was just the rainy day parade.
Now, after 6 PM in the rain, DCA was a GHOST town. Very nearly a walk-on to Toy Story Midway Mania (I still don't LOVE that ride--except smashing plates!--but it was real tempting to just ride it a kajillion times in the rain).
After 9 PM in the rain, even Disneyland was starting to empty out...walked practically all the way to the movie room on Indy with no wait, no wait on Pirates of the Caribbean (some boats actually went through empty), the only wait to speak of on HMH was to get into the 1/3 full stretching room from the lobby.
Entertainment offerings were sparse, though; I don't think they even got the Columbia out of its "dock" area and the Mark Twain appeared to be at its dock all day too. There were pretty big gusts of wind, so no fireworks.
The only thing that kept me from ADORING the rain was that crowds weren't THAT much lighter than Wednesday and Thursday, which had almost perfect weather (a bit chilly is all).