Temperatures: Averages and Extremes

Temperature and the length of the growing season are both critical to the ripening profiles of sugars and acid of the grape and the overall quality of the fruit.

The growing season is the time of the year when crops and other plants can successfully grow. The length of the growing season can be measured in two different ways:

• The number of consecutive frost-free days from the date of the last spring frost to the day of the first fall/winter frost.
• The number of days in the year the average temperature is above the point at which the crop germinates, meaning it can grow and develop. This method is based on the crop so that it can vary due to the characteristics of the plant.
• The length of the growing season for grapes ranges between 170 and 190 days.

The mean temperature during the hottest month is more than 66°F (18.9°F) and the mean temperature of the coldest month is greater than 30°C (-1.1°C). During different stages of development, the bud and fruit are susceptible to damage from extreme cold and hot temperatures. These extremes can kill the bloom or fruit, or cause the fruit to ripen too quickly or not fast enough.