During our current heat spell (97 degrees F yesterday and mid-90’s today) we have had multiple customers ask about the effect on the vines given that budbreak is underway throughout the vineyard. To attempt a coherent answer in regard to this question we will refer to the wise words contained in our trusty Oxford Companion to Wine:
weather, probably the single most exasperatingly unpredictable variable in the viticultural equation, as in most other farming activities.
The precise effect of the hot weather on our budbreaking vines is an acceleration of the growing process due to a combination of the amount of water in the soil given last week’s storm, the fact that we are in the process of turning under cover crops to give the vines a burst of nutrients, and the amount of unobstructed, enriching sunshine the fresh leaves are receiving. If the heat were more extreme (say in the 105-110 degree range) we would be very carefully monitoring water in the vines and soil in order to intervene if they began to cook. The next delicate phase will be as the vines begin to flower. If a heat spell were to hit us hard during the flowering process we would be at risk of reduced yield due to the delicate nature of the flowers and the increased potential for wilting.