At WDW do the waterparks on those really hot days. Or do water rides at the other parks and make sure you get wet.
The other parks I would do early in the day or at night. Hang out by the pool during the midday.
Spray bottles with fans, and drink lots of water. I also like the ice cube in a bag under your hat.
Try one of those wrap around cloth coolers on your neck.
For the exception of waterparks all apply to Disneyland and California Adventure too.
What ever you do have fun and stay
