Hope for the best weather, but prepare for the worst.
If you're used to Disneyland's blue skies or Walt Disney World's one-and-done rain showers, the weather is jarringly different in China. It can get really, really hot and rain nonstop for hours on end. Bring layers, especially a poncho, and be sure to tuck an umbrella in your bag as there isn't much shelter. Even if it doesn't pour, you're still prepared to ride Roaring Rapids!