What is diurnal range?
A. The speed at which yeasts convert the sugars in grapes to alcohol
B. The difference between the daily low temperature and the daily high temperature
C. The difference in elevation between two vineyards owned by the same estate
D. The extent to which a row of vines might shade the row beside it depending on the position of the sun
Diurnal range, or diurnal temperature range, is the difference between the daily high and low temperatures. It doesn’t sound all that sexy, but in fact the diurnal temperature range is crucial to producing great wine. In many of the best wine regions in the world, the diurnal shift can be as much as 30 to 50 degrees within a single day. That means that the vines rest during the cold night (preserving freshness and acidity) but then get to work ripening the grapes during the warm day (creating rich flavors).