I came up with....
+ A fan, any kind, even those little motor powered ones (that would look SUPER cute deco'd haha!)
+ A parasol, or even a simple umbrella to block the sun.
+ And though the smell isn't very loli, sunblock might be nice if your pale and burn easily. (*cough*90%-of-us*cough*) And on that note please use deodorant and or a body spray. T.T
+ As few layers as possible, so a petticoat yes, but no bloomers or very light bloomers/simple shorts
+ Wear regular knee high socks instead of OTK or stockings
+ Short sleeve blouse vs. long sleeve
+ Tea party shoes instead of boots...
+ DRINK LOTS OF WATER. No matter how un-lolita a water bottle is, I recommend one.
EDIT: And I'm going to add this last one in honor of META's line, for the love of loli... choose cotton over latex. XD
Link: http://community.livejournal.com/egl/15318543.html#cutid1 (near the bottom!) It took me almost an hour to hunt down this post. T.T
When I get really hot in lolita I start twirling around, jumping and dancing, it gets some good breeze/air flow going. XD