How Does Climate Affect the Growing of Grapes?

The Ideal Grape Season

• Grapes can be grown successfully in the United States from Florida to Minnesota and from California to New York by choosing the right variety for the region. However, the ideal season to produce exceptional grapes does not happen every year in every region. A cool, wet winter provides ground water, but spring must be warm and fairly dry. Summer is mild with cool nights and no rain leading up to a warm, dry harvest.

Precipitation

• During the growing season when the grapes are forming and maturing, dry conditions produce the most flavorful and sweet grapes. Sugar transfers from the leaves to the fruit during ripening, and growers continually test the sugar content to determine quality. Rainy, wet conditions not only increase the possibility of pests and mildew affecting the vines, but also dilute the flavor and sugar in the grapes.

Heat

• Although grapes prefer warm temperatures, especially during ripening, very hot temperatures can adversely affect maturation. Sustained temperatures above 90 degrees Fahrenheit combined with dry conditions could ripen the grapes too quickly, affecting the color and lessening the quality of the grapes. However, high temperatures can offset the negative effects of excessive rain and vice versa: more rain offsets the negative effects of high temperatures.

Frost

• Although grapes are dormant during the winter and many varieties survive the winter well in colder climates, a late frost in spring or an early frost in fall causes severe damage. In spring, freezing temperatures damage newly opened buds and young shoots, affecting the amount of fruit production later in the season. An early frost in fall just before harvesting can defoliate the vines and severely damage the harvest.