Breeding is always easier if when you follow the natural bio-rhythm of the rabbit. That means that early spring into early summer is going to be the easiest time to get your does to conceive. As you progress further into the autumn and early winter, it gets more difficult, as you are going against the animals natural instincts to reproduce earlier in the year.
From a production standpoint, you need to get younger does into the production cycle before cold weather sets in. Colder temperatures can be mitigated if you have a climate controlled rabbitry, but in most cases this is beyond the economic feasibility of the average breeder. Therefore, you should adjust breeding efforts to an optimum set of circumstances for late year breeding. Set breeding times on the warmest days in your weather forecast.
Allow as much warm time as is feasible when trying to breed. This usually means breeding late in the day so the doe is exposed to the most warmth possible. Try to breed on the later days of a three or four day warm up periods. In consistent colder temperatures, it helps to bring the doe into a warm environment for several days prior to trying to breed.