Definition - What does Winkler Region mean?
In 1938, a well known viticulturist, Albert J. Winkler, developed a classification system to define the different grape growing geographic regions in California. The Winkler unit of measure is the “degree-day”, which is found by calculating the number of days between April-October that have the best temperatures for growing grapes. This system is divided into five regions, which are determined by the region’s heat level also known as “heat summation regions”. This system has been critiqued and revised but is still in use today.
WineFrog explains Winkler Region
The Winkler regions are divided into five different sections, (I-V throughout the state of California) each having a certain number of “growing-degree days” specific to their heat index. ‘Degree days’ or days that have temperatures over 10O C, which is the climate in which vines start to grow, are recorded over a seven-month period. The most premium vineyards and grapes are nearly always found in climates that have a narrow temperature range. This narrow range is characterized by a lack of extreme temperatures and constant mild conditions excellent for growing quality grape vines.
Regions I (the coolest and most constant) and II contain the least amount of growing-degree days and generally produce the best and dryer table wines. Region III is best for sweet and dry, full-bodied table wines. Region IV’s climate produces fortified wines and Region V has the highest number of degree days producing the lowest quality table wine.