weather, probably the single most exasperatingly unpredictable variable in the viticultural equation, as in most other farming activities. For details of overall weather patterns, see climate, macroclimate, and climate classification. For accounts of specific climatological phenomena with implications for wine production, see dew, drought, flooding, frost, hail, rainfall, sunlight, temperature, and wind. The weather in a specific growing season is the most important influence on the characteristics of a particular vintage year.