We know that rain just before harvest can be risky for wine. Here is a primer:
Why does rain matter? Rain can do a few things to grapes that we worry about: 1) Rain can split berries, which opens them up so microbes can enter the berries, increasing the risk of spoilage; 2) Rain can create rot or botrytis, which is just straight up not good; 3) Rain can dilute flavors or get the sugar/acid ratio out of balance.
What can we do about it? There are things we can do in the vineyard and winery to combat this: 1) In the vineyard, we have already have done botrytis sprays at critical growth stages earlier. We could do another spray, though the data indicates this is of questionable value; 2) We pull leaves to open up the fruit zone, which allows increased airflow and helps dry the grape clusters out; 3) Once the grapes come in to the winery, we sort like crazy on the sort table, trying to get all split berries, rot and botrytis out; 4) We increase the amount of sulfur dioxide added to inhibit any bacteria that may occur. As a reminder, sulfur naturally occurs in wine, but sometimes conditions require a boost.
Are you worried about it right now? I am not very concerned at this point. We had terrific sunshine during the growing season which allowed us to get to near full ripening, so all we need is another week or two of development and some dry days to dry out the clusters and allow for harvest.