We have been going at that time for approx. 10 years, for 2 weeks, so we know it well!
Weather - hot and humid! Despite what everyone thinks, it does not rain each day. The past few years, we have had days on end where it didn't end, and this year (we went 1 week earlier), was our coolest July ever! It was hotter at home! That being said, you need to take frequent breaks, especially in the air conditioning, drink, drink, drink and wear hats. Also as mentioned, misting fans are great! We take lots of shopping breaks, eat in restaurants and take a daily mid-day break to swim and freshen up.
Parks - they are open early and stay up late. Nothing is better than to be strolling around World Showcase around 8:00 pm, when the humidity has gone down, and there aren't that many guests around. MK is open very late many nights, so you can get a good amount done that way.
Crowds - they will vary. As I said, we are July experts, and have been at Christmas/NYE and March Break, and July crowds vary. Some days very busy, and others, not so much. The crowds are generally heavier though, so expect long delays at certain attractions, so you must use Fastpasses. I won't speak too much about tour groups, as we haven't had many issues with them at all. There are lots of tour groups in the summer though: schools, families, etc., so be mindful of larger groups of guests waiting in lines, and go the opposite way!
Hope you have a great time. See you there! Tiger
