When is the heat period of a male rabbit?

Male rabbits are "in heat" 98% of the time. In other Words, there is no heat period. If it is really cold outside and they are in an outside hutch it is natural instinct NOT to breed.

Rabbits don't go into heat (neither males or females): they're ready mate at any time. (The females don't ovulate in a cycle, like humans - instead, they ovulate in response to sex.)

Animals tend to want to mate when there's the best chance of food and shelter for their babies. That's why so many animals mate in the spring: there's plenty of food around, the weather is nice, and there's lots of fresh foliage to hide your babies in. So, the wild rabbits in any given place might mate more often at certain times of year than others. But they're capable of mating all year 'round.