If you have clean vineyard, but you still have more than 10 days to go, it may depends on the condition of the berries. If you notice any wounding on berries (by birds, hornets, sun damage, etc), then you may want to consider captan before this rain because many of late season rots take advantage of these wounds. If you have nice clean berries, then, you may able to wait and see.
If you have some rot issues, again captan is a nice tool. It is effective against variety of pathogens, and it has a very short PHI (0-day) (but remember that REI is 48-72 hours, depends on the formulation).