They announce it in the newspapers here in Germany. The harvest has started. Bacchus in particular. We have Bacchus (a bit, – the main bits are Silvaner, which ripens later). We are not harvesting right now. The Bacchus tastes yummy though, so clearly on its way.
To be more scientific, here are the pips. We have three bits within the “motorway of vines”, “3 Stueckerl”, Silvaner, Silvaner and Bacchus. That’s the order of the pictures below. The pip turning brown is an indication of ripeness. As I said, all very scientific. I would call the last pic halfway between green and brown. So even our Bacchus has a bit to go. Phew. We would not be ready yet.