These vineyards have slow maturing fruit. Do not rush this fruit to harvest, it could come around later in August. All growers should have already started checking their sugar levels. The should also have an estimate on their crop size by variety. I like to use whole cluster sugar testing, and do it to at least five vines in any one block for each variety.
Some wine makers like to use single berries and cover many more than five vines.
I like to count the number of clusters on each of the vines, weigh the clusters and multiply the number of vines to determine the estimate of tonnage. Do not use the largest clusters, pick an average to less than average for both the sugar and the weight. The heavy rain slowed the symptoms early in the season. The cold winter could have also held it back in some vineyards. By mid August we should know much more.