Same time we usually go.
Weather - extremely hot and humid, temps in the mid 90s a lot of the time.
Getting to the parks early is a must as well as planning plenty of rest days too, it's just too hot to spend hours and hours walking around all day.
Taking breaks indoors and drinking plenty of water is essential.
I suppose it depends on how many days you visit the parks and what time you visit, to be honest we just spend a few hours in the morning, I don't mind the heat that much and certainly would prefer it hot than cold, but Julie and Joshua struggle a bit so we need to be careful.
Crowds - generally quieter from the middle of the month as many of the US schools return. However, Disney (in their wisdom) introduced the
DDP ,
Disney Dining Plan (daft dining plan I call it), which has kind of made crowd levels more difficult to predict.
There will be less crowds than say July but not as quiet as it would have been pre-DDP days.
For many people the DDP is great, but Josh isn't a big fan of eating out plus summer being the only time we can go means it's expensive and very hot as I say above.
The fact the crowds were not that bad was a plus point as heat & crowds personally I find hard work, the DDP has kind of put a 'spanner in the works' as whilst it's by no means busy it's definitely busier than it used to be.