It is HOT.... VERY HOT! The sun is VERY strong, so please, please, PLEASE wear that sunscreen. Especially put it on the children, even those in the strollers, because the sun's rays will reflect from the pavement into the stroller and give them an awful burn! I have seen too many down here in the past 2 weeks!
Drink plenty of water and sports drink. Avoid sodas and alcohol, as they dehydrate you.
Invest in a mister fan and neck cooler, and jump in the interactive fountains as often as possible.
Seek shade and air conditioned attractions in the middle of the day. We usually plan our big meal in the middle, hot part of the day to unwind and relax.
Do you touring in the early mornings and later afternoon and evening.
Wear loose fitting clothing. Comfort here is paramount. No one is looking at what anyone else is wearing... they are too busy trying to stay cool themselves!
If there are little ones, please give them an opportunity to rest, relax and chill out. It is so sad to see an overtired child who is understandably cranky and the rest of the family just pulling him/her along anyway. No one has any fun that way! Go back to the resort and take a nap, or rent or take a stroller, so the child can nap while the rest of the family tours.
MOST of all, have a safe, non stressful and relaxing vacation (like that can be done in WDW

)... remember, you can't see it all, so just see the highlights and go with the flow!. Have a GREAT time!
