Diurnal Temperature Fluctuation

The difference in temperature from the coolest point in the morning to the warmest point in the afternoon. A large difference between these two temperatures is ideal for wine growing regions as it allows the sugars to ripen during the heat of the day while the natural acids are preserved thanks to the coolness of the night. In regions such as central Spain, Napa Valley, California, and Mendoza, Argentina, the daily diurnal temperature fluctuation can be as much as 30 to 40 degrees Fahrenheit.