Veraison is moving along quite well. As of yesterday, Marquette is about 40% complete, Frontenac is 20% complete, and Foch is just under way in the last few days.
I went over my records the last few years to try to better predict when veraison and harvest would occur. Several factors determine the timing of different phenological events in the season; such as vine health, precipitation timing, nutrient availability, cultivar selection, temperature etc. For simplicity I am going to use GDD(Growing Degree Days base 50F) since, for the most part, it can be measured more objectively and I have a pretty good temperature history during the last 5 growing seasons.
In my cultivars, bud break occurs between 100-200 GDD (using accumulated GDD from March 1). But this varies significantly from year to year, since springtime warm and cold waves can mess with the timing of things. This year bud break was at ~200 GDD on May 6.
Rose Chafers seem to appear at about 450-500 GDD (also measured from March 1). This year they appeared at 497 on May 29. This is the earliest arrival since I've had vines planted.
For veraison and harvest I use accumulate GDD from the date of bud break to eliminate spring weather fluctuations.
In my vineyard, veraison typically occurs at about 1,450-1,600 GDD This year it began at ~1580 GDD on July 23-26. Marquette is usually first to begin veraison, followed a few days later by frontenac, and then a few more days later by foch.
In 2010, harvest was between 9/5 and 9/11 with GDD closer to 2,200. Last year's harvest was on Sept 24 with 2,145 GDD, This year, if August has near normal temperatures, we should reach about 2,200 GDD by August 25!