I'm from the northeast.
School typically starts on Tuesday or Wed after Labor Day. I was banking on that last year, and in July they changed the start date for the first time in anyone's memory to before Labor Day...so my kids missed 7 days of school instead of 3.
This year schools starts after Labor Day.
Last year, 2015, we were there the week before and the week after Labor Day. (I have the same schedule this year) The second week was noticeably less crowded than the first week. We were in AK/MK on the Saturday of Labor Day weekend. AK was crazy crowded compared to the other days of the trip. While we were there they made an announcement extending the park hours. We went to MK around 730. We had no patience for lines and could not get a single fast pass, so we just waited for the parade, snacked and people watched. After the parade, the park emptied out. park closed at 12am EMH until 2am. That was fabulous - -DD met Anna & Elsa with a 5 minute wait (posted time was 40 minutes, but no one was standing in line that we could see - -CM told us to go in that there was a 10 minutes wait max), and then 15 minutes for Cinderella & Rapunzel. Everything was pretty much a walk on after midnight, but I didn't check the mine train, so not sure if that was.
Sunday of Labor Day weekend was our laundry/rest/hang at the pool day.
Monday we went to a Typhoon Lagoon -- it was less crowded then the Sunday before Labor Weekend.
Labor Day weekend is most definitely more crowded that the days preceding or following it in my opinion, but in terms of Disney crowds, it's not bad. However, I do plan to avoid most of the weekend if I can. We plan a water park again on Labor Day. This time we are going to use Saturday as our rest day and try Sunday of labor day weekend instead - -same thing AK in the morning, MK in the evening saving our FP for MK this time - -just parade & fireworks, and if the rides are doable great, if the lines are too long, we have 3 other days at MK to ride them.
YES IT IS HOT!