You can find cover in Diagon Alley and Hogsmeade in the restaurants and shops. The line for Forbidden Journey is mostly under a roof and the ride is inside. You can also ride Hogwarts Express which is inside. Many of the other rides at universal are inside but obviously the coasters and some of the outside rides might be closed. Get some ponchos and I think it will be okay.
You should be just fine. Like Ryan stated there is a lot of places that are indoors till it passes
Wet
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