Can roof be repaired when it rains?

We have a 1940 brick and tile house. This winter it rains a lot in Auckland. Part of the roof is leaking and the celling is moulded. one builder came in check it. There are gaps between tiles because the wooden structure slightly changed shape for whatever reason. But he said it can't be repaired until its completely dry out and the repair need to be done in fine days as well. The rains is not likely to stop for a week or two until summer comes, which is months away. Do I have to wait to acheive a good repair result? I worried by that time, my celling & all the insulation also need to be changed completely.