Well, I can tell you about Texas hot. It's 113 sometimes (and I'm not even in South Texas)
I set up a misting system that hits about 1/3-1/2 of the cage. Most of the rabbits love to lay in the mist, even the bitty ones.
I have Tamuk rabbits that are bred especially for the heat, so I don't turn the mister on until it's 90'. Then I have a water timer that turns it on at intervals, depending on how hot it is. Somewhere on rabbittalk I saw a really nifty set up with a mister/timer all automatic. Mine's not that fancy.
If I had 'normal' rabbits, I might turn it on at 85 or even 80. I'm not sure how hardy they would be.
My rabbits must be pretty comfy, they don't pant & I did have a couple healthy rabbits die when they got to their new home and weren't as pampered. (I won't be breeding in the summer again, I think it's too hard on the kits to adjust to new circumstances in the heat)
Hope that helps. I keep meaning to write an article for my website, someday I might get around to it. Glad to answer any questions if you have any