Vintage 2020: May Cold Temperatures

This weekend, we were crossing our fingers due to the unusually cold temperatures we were expected to have on Saturday morning and Sunday morning. My husband has a HOBO data logger and we went to the vineyard on Saturday and downloaded the temperatures as well as check on the buds that were coming out of dormancy and potentially susceptible to cold temperatures.
The HOBO showed that during the morning hours on May 9th, the temperature hovered between 30 - 32^o F between 2:30 and 6:00 a.m. The young buds seemed to have faired okay on Saturday morning, but there was still Sunday morning's forecasted cold temperatures to come. We did the same exercise on Sunday afternoon, downloaded the HOBO data and took photos of our various buds. My husband told me that on May 9th, from 8 p.m. into the morning hours of Sunday, May 10th, the temperatures varied between 34 and 32^o F, until dawn, when at 7:20 the temperatures climbed to 45^o F.
Our tender buds seemed to have withstood the cold onslaught.
Here are some photos taken on May 10th:

Variety	Budbreak Stage
Auxerrois
Chenin Blanc
Chardonnay
Cabernet Sauvignon
Cabernet Franc
Barbera

We were relieved that our young buds survived Mother Nature's late winter blast and then wondered what freeze does to a grapevine. One of the sources that I refer to time and again when there are freezing conditions is this: Understanding and Preventing Freeze Damage in Vineyards ~ Workshop Proceedings ~ December 5-6, 2007 University of Missouri-Columbia. On the right, you can see what happens when a freeze occurs during budbreak.
The vine was at E-L stage 7 which is described as "first leaf separated from shoot tip". The photo shows that the apical bud was affected but the next bud survived. Unfortunately, there was no information regarding what day the photo was taken and the temperatures that caused the bud to freeze.
Most of the information on freezing, refers to winter freeze in grape vines and I have written a few blogposts on that:

• March 9, 2018: Freezing Conditions During Spring Grapevine Deacclimation
• April 24, 2015 Spring Bud Deacclimation and Cold Weather
• February 6, 2015 Grapevine Cold Hardiness
• February 4, 2014 Cold Hardiness of Grapevines Through Cold Acclimation
• November 11, 2012 Winter Injury to Grapevines and Methods of Protection
• November 10, 2011 Cold Tolerance and Grapevine Phenology

We have two more days with low 30's morning temperature, so fingers still crossed!