It won't be fun on a rainy day. When we were there it was threatening rain and they said they would close the rides if there was going to be lightning. Even with just rain, it wouldn't be much fun.
A rainy day would not be good. Everything will be muddy.
They do not generally close if it rains unless the rain is really bad (like terrential downpours). I personally think it's worth it to go if you have your rain gear. You'd be able to get on rides a lot faster because of the lack of lines.
Don't go on a rainy day. Everything is outside.
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