We used to go to WDW in middle June and August for the extended hours but the heat is terrible. That was 20 years ago and the last 5 years, we go either October, December or May. Weather is great, can hit a cold spell but haven't yet. This year, October 13-23 at the Poly again. Really like the October time, its fall in the north and traveling south is great, we go by Amtrak the kids are back in school and the parks seem cleaner, less crowded and the air crisp and fresh with the coming of Florida winter. Seems less hectic and its easy to get around, but it also seems that other WDW guests are finding this time of year great also, the summers are way too crowded and really super hot but the first week of December is like going in February, hardly no one, everyone is waiting to go at Xmas time and the Xmas decorations are the best anywhere and are up through November till after Xmas.