temperature variability, a characteristic of climates referring to the short-term variability of temperature between night and day (diurnal temperature variation or thermal amplitude), and from day to day. It is unrelated to annual temperature range, as described under continentality, and clearly distinct in its viticultural and oenological implications (see temperature). Temperature variability plays an important role in determining the risks of frost damage to dormant vines in spring and autumn, and of heat stress and direct heat damage to the vines and fruit in summer. Gladstones speculates that restricted temperature variability is important for improved wine quality in cool regions since it may influence the formation of pigment, aroma, and flavour in the vines and ripening berries: these processes being favoured, relative to the mere accumulation of sugar in grapes, by a narrow daily temperature range and minimal temperature fluctuations from day to day. However, in warm to hot regions, a greater temperature variability may be an advantage for wine quality as it implies cooling effects at night (see climate and wine quality).