As a child of the tropics, the Christmas cactus is not hardy. But since it blooms in winter anyway, it is overwintered indoors. So there is no risk of him freezing to death. You do not have to hibernate Christmas cacti, but oversummer.
The Christmas cactus blooms in winter but is not hardy
Christmas cactus do not overwinter, but oversummer
The Christmas cactus blooms from late November to January. It is kept indoors during this time for you to enjoy flowering. So there is no danger that he will freeze to death in winter in the frost.
You don't have to hibernate a Christmas cactus, you should oversummer it. During the warm season, it enters a rest phase in which it is watered less and kept cooler overall.
tips
In summer you are welcome to take care of the Christmas cactus outside. Find a spot that isn't too sunny. Also make sure that the root ball does not get too wet when it rains.