Always a bit of a tricky question. Some folks will wear shorts as low as 30 degrees, while others wear long pants even when it is 90.
Here’s what I can tell you. Many women wear skirts/sundresses at WDW, but in the parks you’ll have to climb into multiple rides if you want to go on them. Astro Orbiter and the boat rides come to mind.
When it comes to dining, dresses and skirts are much more common, especially for signature dining and formal events. WDW hosts many weddings and formal events in their many ballrooms every day. On any given WDW day, odds are good that you’ll see quite a few wardrobe extremes!
There IS a dress code in the parks and when dining, but it is fairly lax. You can’t wear anything that is deemed to be offensive. For the ladies, well…I’d say most ladies think “family friendly’ when choosing park attire. You also aren’t allowed to imitate a cast member at any time, and there are limit on costumes, especially for adults. I think you can find the specific rules pretty easily.
Most character dining the dress code is fairly minimal, but it is a little more strict for signature dining. Those that are rated $$$ on WDW’s website. At the moment, only the Cinderella castle character meal comes to mind. On the other hand, most folks take LOTS of pictures at character meals. Sometimes we freshen up before dinner, especially if we’ve been swimming or went on a wet ride.
Kali is the wettest ride at WDW. Splash is mildly wet. Good to avoid denim and sheer whites on either. Universal also has several very wet rides.