We went this week in 2005. the weather was perfect. 70's & 80's sunshine with no humidity or rain.
It is, however, Jersey Week which means the Parks are a little more crowded than the week before or after the 4-10. Don't panic and cancel your trip because it is Jersey Week, it is very manageable if you use a touring plan and get to the parks in the morning. (do a search for Jersey Week and you'll find numerous discussions about it.)
If you are in your early planning stages and can go the week before or after this the parks will be quieter and the weather not much different.
Overall the parks are not that busy this time of year. Line ups rarely more than 30 minutes and with use of FP's and a touring plan we NEVER stood in line more than 10 minutes all week.