Not sure about the cooling part, but when you breed you will probably need to do a day and night cycle. And when to breed, you could probably try to do it during the Summer time, but I don't think you'd be very successful. I think it would be best to do it from Sept. to Feb.
Can you breed your Leo's anytime during the year or is it only from Feb to Sept?
Daniel
Edit: Also do you need to cool your leo's. If so for how long?
For the most part they breed from Feb-Sept or Mar-Oct or so.They might breed outside of that but probably won't. You do not need to cool them. Put a male and female together and they will breed. They may bite each other and leave marks on each other but don't let that worry you. You shouldn't breed a female year after year. Give her a rest every other year or two.