As with any other crop, the grape harvest is the period of time when the grapes that are to be made into wine are picked. Not only must the grapes be physiologically ripe, the winegrower must also consider the threat of impending weather, logistics between the vineyard and the winery (including, among many other variables, the availability of muscle power and winery equipment), the temperature of grapes during picking and transportation to the winery, and the method of picking the grapes (either by hand or machine). Also of importance is the style of wine to be made. For example, in order to preserve the high level of natural acidity essential for sparkling wine, Chardonnay and Pinot Noir grapes intended for its production are typically harvested much earlier than the same grapes when used for still wine. Travelers beware: During harvest is probably the worst time to visit the wine country if you want good service at the winery, unless you have prearranged to help with the harvest.