Growing season length is another critical parameter for vineyard site selection. Jordan et al. (1980) classifies sites as Unsuitable (< 165 days), Marginal (166 - 180 days), Preferable (> 180 days). They defined growing season as the number of consecutive days where the minimum temperatures is above 29oF. For this study it was defined as the numbers of days between the last occurrence of 29oF or less in spring and the first occurrence in fall. In most of the state the growing season is too short for viticulture, whilst even in the more recognized viticulture regions the length must still be classed as marginal. The mean may be expected to vary by about 25 days, so that in many seasons the growing season will be especially short.
The majority of the state has fewer than 163 frost free days. The Great Lakes, St. Lawrence, Finger Lakes and valleys of Western and Eastern Plateau have between 170 and 176 days. Some areas within these regions that have an additional week due to their proximity to water bodies, notably in Niagara and Monroe Counties along the south western shore of Lake Ontario and on the eastern shore of Seneca and Cayuga Lakes. The Upper Hudson has less than 176 frost free days but the lower reaches and Long Island have more than 190 days. The standard deviation on the mean length of frost free days is approximately 25 days and varies little across the state except at higher elevations.
Methodology for construction of climatic maps