Degrees in Fahrenheit (10 degrees Celsius) at which physiological processes begin to take place in a grapevine. Below this temperature, a grapevine is dormant. Drastically below this temperature—below 32 degrees F for example—a grapevine might suffer considerable damage or even die. When the average daily temperatures reach 63 to 68 degrees F, vines will begin to flower. And when those average temperatures reach 80 degrees F, (as is the case now in the northern hemisphere) the grapevine is in full stride, and grape clusters can begin ripening.