GDD base 50 = 93. 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
After three nights with temperature in the 20s, April 20 to 22, there was damage on the grapes. It was difficult to estimate today, but we think that in general, 50 to 70% of the primary shoots were killed. NC-6, Traminette, and Vidal Blanc were the least developed and it looks like Traminette and NC-6 have more live buds than other cultivars, but once growth begins again, we can assess more accurately.
| Month | Day | Year | Min Air Temp F | Min Dew Point F |
| 4 | 20 | 2021 | 28.0 | 25.5 |
| 4 | 21 | 2021 | 24.5 | 16.1 |
| 4 | 22 | 2021 | 25.4 | 13.4 |
The minimum dew point was below the minimum critical temperature, indicating a black frost which is more damaging.
I did not upload the photos since they were a “freeze-dried” version of the phenology stages recorded last week.