I don't have as much experience as most on this board, but we were there the last week of June last year, and I did not think it was that bad. The park was waaaay more crowded than when we went in January, but I swear the lines went faster. I think I heard someone mention that they have more cars/boats in rotation on the rides during busier times, so that may have been why.
It was extremely hot, but we had a stroller packed with FROZEN water bottles and that was a life saver, just holding one would cool me off. We did Magic Kingdom from morning til night, but we took lots of mini breaks soaking up the air conditioning at the counter service places.
I would still go if I were you....we managed to have a blast and we were a family of 6 adults and 3 kids in strollers, but we're all goofy and get along great.
Also, I don't think I'd like AK in the heat. We went when it was cool and loved it, but I think it would be miserable with it's narrow pathways and tropical rainforest feel.
Hope this helps!
