Rabbits (of any sort, doesn't matter if they've got lop ears) really don't tolerate temperatures greater than 80 degrees, since the only parts of their bodies that radiate excess heat are their ears. What I would do is stick some water bottles in the freezer, and put one in each hutch if the temps got too high.
However, I'd really re-think leaving them outside. Even in a hutch, just the mere presence of a predator can give them a fatal heart attack. There are a few things you can do to cut the smell down:
1) Make sure the rabbit has been spayed or neutered. Just like cats that are intact, intact rabbits will spray to mark their territory, especially once they hit puberty.
2) What type of litter are you using? Yesterday's News and Carefresh are made of paper, which is more absorbant than wood shavings (which aren't really good for rabbits anyway, since the fumes they emit can damage their livers).
3) There's also a substance called Ammo-Sorb which you can find in several pet stores as well as the pet section of many supermarkets. It looks like white cat litter. Pour it on the bottom of their litter box/cage, then put fresh litter on top. The ammo-sorb does just what it says - it absorbs/neurtalizes the ammonia in their urine, which means that you can go much longer between complete litter changes. You'll still have to refresh it every day or so, but using the ammo-sorb has given me anywhere between a week to 10 days between complete cleanings.
4) Every three weeks to a month, pour full strength white vinegar into their litter pans, and let them soak for about 30-45 minutes. It will sanitize them and remove any lingering hardened waste.
Hope this helps.
