If you're interested, I looked at historical weather data for the week we'll be in DLR in my PTR (link in my signature). On page 2, about a quarter of the page down. I listed the page I used to gather that data. Yes, I'm an old weather guy who likes digging into that kind of stuff.
I've always been fascinated with peoples perceptions versus reality, when it comes to weather. A few years ago I read a study where people were convinced it rained more on the weekend. Someone surmised it was because of cars and pollution and that emissions from commuting through the week "built up" to cause more rain. A group went through and looked all of the rain data on record and determined it did not rain more on the weekends at all. It was people's perception that is did because they were trying to do fun stuff on the weekend and getting rained on. Long story, but that's why I like to look at the actual historical numbers to see what "normal" is supposed to be.
That said, anything can and will happen. For us, I'll start watching the weather forecast for the area a week or so out. I try to look at various forecasts, because they're all a little different. National Weather service based forecasts tend to be the most pessimistic. Accuweather forecasts are typically most optimistic. The weather channel (as much as I've grown to dislike their sensationalism) is typically somewhere in the middle with their forecasts.
I can tell you that in all of the historical data I looked at, the one thing that jumped out at me was the typically low humidity. Low humidity is going to do 2 things for you; you'll see cooler evening-night-morning temperatures and high temperatures will feel more comfortable than when humidity is high. Anyone who has been to WDW in late July can tell you that higher humidity translates to the opposite; relatively warm overnight temps and instant sweat heat during the day.
