GDD base 50 = 3613. We track GDD at http://agebb.missouri.edu/weather/reports/gddTable.asp and rate the phenology stages according to the Modified E-L System http://door.uwex.edu/files/2010/10/ModifiedEichhornLorennzsystem.pdf Warmer days and cool nights help the grapevines acclimate properly going into winter. … [Read more...] about Grape phenology and GDD accumulation