A continental climate, tempered
What made Dr. Konstantin Frank, a professor of plant sciences who held a Ph.D. in viticulture, choose the Finger Lakes when he immigrated to the US in 1951? For one thing, the climate is decidedly continental. Which means that it is marked by significant temperature variations between the winter and summer months (as opposed to the more mediterranean climate of California, where summer months are hot and dry and the winters are mild). In the Finger Lakes region warm summers are usually followed by very cold winters. Some of the most famous wine regions on this planet are so-called cool climate regions: Burgundy and Champagne in the north of France, the Mosel region in Germany. In the Finger Lakes the average temperatures in January are even below those in the Mosel region - almost too cold for viticulture. But Dr. Frank saw more than just bare numbers. He saw the moderating effect that the lakes have on the region's climate.
Air drainage
Carved out by ice masses over millions of years, the deep canyons filled with water after the glaciers' withdrawal during the last Ice Age roughly ten thousand years ago and eventually became today's eleven lakes. Long and narrow they lie next to each other like fingers of a hand and thus gave the region its name.
Cayuga and Seneca are two of America's deepest lakes and as such have a significant impact on the microclimate. Without these large bodies of water viticulture would be near to impossible in this cold climate. Their influence on the vineyards is crucial at two points of the growing season.
Foremost in the fall, during the end of the growing season, when the grapes accumulate their sugars and flavor compounds. The lakes store the heat of the sun and create a so-called air drainage. As the warmer air above the water surface rises, it creates a gap which is filled with the heavier cold air, which thus drains off the vines.
The influence of the lakes on the vines is of opposite effect in the spring. The lakes, still cold from the winter months, cool the vineyards as general temperatures rise in the vineyards. In cool climate wine regions, late spring frosts are a major hazard every year. They can kill the still tender buds and the vines won't produce any fruit. The cold lakes delay the budding of the vines and thus protect them from possible late spring frosts.
The soils around the lakes are quite varied, ranging from well-drained sandy loam to iron-oxidised red clay. The bedrock underneath can be calcareous or non-calcareous, thus having a significant influence on the acidity level of a particular vineyard.1
1 Soil Acidity in Vineyards of the Finger Lakes of New York, Benjamin Linhoff, Boise State University 2005