It's been a long growing season. The last drink they had was in the spring. They are full of sugar and the berries are concentrating their trademark flavors.
Harvest is near.
Probably next week, acid is still a bit high. The weather is supposed to be pretty warm this weekend, so it could be early in the week.
In the meantime, the entire Sonoma County begins to have the slightest waif of fermenting grapes in the air. It's harvest season!