Once temps get into the mid to upper 80’s I would advise not to breed. It’s too much stress on the doe, as well as the kits. When breeding in winter it’s important to protect the rabbits from the cold wind. We would hang heavy tarps around our cages to protect them. As long as the kits are well insulated with hay/straw & the doe’s hair, in a nest box, they should be okay. If temps got in the 20’s we would sometimes hang a heat lamp outside the cage, pointed towards the box, to help.