The Disney app or the Disney website all let you know on advance.
They were when i was there
Last week avatar and the rapids were closed
As of today (5-5-18) there's only a couple spots in the park that are undergoing some renovations, but they're very small areas and do not detract from the experience whatsoever. All rides are open and operating normally, however like it was previously mentioned - check the Disney Go app for current wait times and/or closures.
Last week mount Everest was close.
It can change at any moment this is based on maintenance and some unknown factors
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