Heat doesn't bother us, but crowds are a drag.
We usually take the girls out of school the last week of the semester, this year it'll be dec 10-17, get back for the last day of school to pick up any paperwork we missed. They never do anything important the last week of either sememster, it's all parties, wrapping up and goofing off.
We used to go during the last week of august when they were younger, but now they start school Aug 14 (stupid georgia rules).
We did the last week of the semester thing in spring, May 17-22, and the 17-20th were fantastic-our best day ever in MK, but on saturday, whoa, crowds out the wazoo! Came back for the last two days of school, and shocker, girls hadn't missed a thing and the teachers were completely fine with them missing school at that time. No tests, no reviews, etc.