With all due respect to Eastern, all but the last half minute or so of the Spaceship Earth line is outside, and although half is in the shade, it's still pretty hot. Long inside lines at Epcot include Finding Nemo and Frozen, although Frozen's outside portion can get long. At MK your best bets are Peter Pan, Small World, Pirates, and Little Mermaid. Also consider the other shows: American Adventure (Epcot), Philharmagic and Tiki Room. At Studios, Toy Story Midway Mania, or hang out in Launch Bay or Walt Disney: One Man's Dream. We were at AK one day when it was 96 degrees and we were miserable; we avoid it entirely June-September. Also, remember that anything without a roof will shut down if there's lightning in the area, so ride coasters, Dumbo, etc. in the morning before the afternoon monsoon hits.